U.S. patent application number 10/520860 was filed with the patent office on 2006-05-18 for autostereoscopic projection system.
Invention is credited to Thomas Bruggert, Markus Klippstein, Stephan Otte, Ingo Relke, Bernd Riemann.
Application Number | 20060103932 10/520860 |
Document ID | / |
Family ID | 30118724 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060103932 |
Kind Code |
A1 |
Relke; Ingo ; et
al. |
May 18, 2006 |
Autostereoscopic projection system
Abstract
The invention relates to an autostereoscopic projection
arrangement, comprising at least one projector (4) and at least one
filter array (F.sub.1, F.sub.2), which has a multitude of filter
elements arranged in columns and rows, in which arrangement bits of
partial information from views of a scene or object are projected
by the projector/the projectors (4) onto a projection screen (3),
where these bits of partial information are rendered on image
rendering elements and, having passed one or several of the filter
arrays (F.sub.1, F.sub.2), are made visible to at least one
observer (5), and in which, as regards the propagation direction of
the bits of partial information, the image rendering elements
correspond with correlated filter elements in such a way that an
observer (5) will see predominantly bits of partial information
from a first selection of views with one eye and predominantly bits
of partial information from a second selection of views with the
other eye, and thus will have a spatial impression.
Inventors: |
Relke; Ingo; (Jena, DE)
; Otte; Stephan; (Jena, DE) ; Klippstein;
Markus; (Munchenroda, DE) ; Bruggert; Thomas;
(Jena, DE) ; Riemann; Bernd; (Ranis, DE) |
Correspondence
Address: |
PATTERSON, THUENTE, SKAAR & CHRISTENSEN, P.A.
4800 IDS CENTER
80 SOUTH 8TH STREET
MINNEAPOLIS
MN
55402-2100
US
|
Family ID: |
30118724 |
Appl. No.: |
10/520860 |
Filed: |
July 11, 2003 |
PCT Filed: |
July 11, 2003 |
PCT NO: |
PCT/EP03/07620 |
371 Date: |
January 11, 2005 |
Current U.S.
Class: |
359/462 ;
348/E13.03; 348/E13.033; 348/E13.035; 348/E13.043; 348/E13.058 |
Current CPC
Class: |
H04N 13/31 20180501;
H04N 13/351 20180501; H04N 13/354 20180501; G02B 30/26 20200101;
G03B 21/62 20130101; H04N 13/312 20180501; H04N 13/324 20180501;
H04N 13/359 20180501; H04N 13/365 20180501; H04N 13/363 20180501;
G03B 35/24 20130101 |
Class at
Publication: |
359/462 |
International
Class: |
G02B 27/22 20060101
G02B027/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2002 |
DE |
202 11 612.3 |
Dec 3, 2002 |
DE |
202 18 862.0 |
Dec 16, 2002 |
DE |
102 59 968.8 |
Claims
1-40. (canceled)
41. An autostereoscopic-projection arrangement, comprising: a first
projector, and a first filter array having a multitude of filter
elements, in which the projector projects bits of partial
information from views of a scene or object onto a projection
screen, where the bits of partial information are rendered on image
rendering elements and, having passed the filter array, are made
visible to an observer, and in which the image rendering elements
correspond with correlated filter elements, as regards the
propagation direction of the bits of partial information, in such a
way that the observer will see predominantly bits of partial
information from a first selection of views with a first eye and
predominantly bits of partial information from a second selection
of views with a second eye, so that the observer perceives a
spatial impression.
42. The autosteroscopic projection arrangement according to claim
41, further comprising: a second projector, a second filter array,
in which the first filter array is arranged between the projection
screen and the projectors, and the second filter array is arranged
in front of the projection screen and in which the first and second
filter arrays have wavelength filter elements arranged in columns
and rows that are transparent to light of different wavelengths or
different wavelength ranges and in which the projectors project
bits of partial information from views of a scene or object through
at least one of the first and second filter arrays and onto the
projection screen, so that bits of partial information of the views
are made optically visible on the projection screen in combination
or mix determined by a geometry of the arrangement, and the
projection screen is divided into a grid of image rendering
elements which are arranged in columns and rows and, depending on
the embodiment of the filter arrays and the projectors, radiate
light of particular wavelengths or wavelength ranges, with each
image rendering element rendering bits of partial information of at
least one of the views, and in which the second filter array
arranged in front of the projection screen defines propagation
directions for the light radiated by the projection screen toward
the observer, in which any individual image rendering element
corresponds with several allocated wavelength filters of the filter
array, or one wavelength filter of the filter array corresponds
with several allocated image rendering elements, in such a way that
a straight line connecting a first centroid of the cross-section
area of a visible portion of the image rendering element and a
second centroid of the cross-section area of a visible portion of
the wavelength filter represents one propagation direction, so
that, from every viewing position, the observer will see
predominantly bits of partial information of a first selection of
views with the first eye, and predominantly bits of partial
information of a second selection of views with the second eye, so
that the observer perceives a spatial impression from a multitude
of viewing positions.
43. The autosteroscopic projection arrangement according to claim
42, in which each of the filter arrays contains wavelength filter
elements arranged in a specific grid assigned to it, consisting of
rows and columns, which are arranged on the filter array depending
on their transmission wavelength or their transmission wavelength
range according to the following function: b = p A - d Apq q A - n
Am IntegerPart [ p A - d Apq q A - 1 n Am ] , ##EQU11## wherein
(p.sub.A=p) is the index of a wavelength filter in a row of the
respective array, (q.sub.A=q) is the index of a wavelength filter
in a column of the respective array (F.sub.A), (b) is an integer
that defines one of the specified transmission wavelengths or
wavelength ranges for a wavelength filter of the filter array in
the position (p.sub.A,q.sub.A), and may have values between 1 and
b.sub.Amax, (n.sub.Am) is an integer greater than zero that
corresponds to the total number (n) of the views (A.sub.k)
displayed by the projectors, (d.sub.Apq) is a selectable mask
coefficient matrix for varying the arrangement of the wavelength
filters on the respective array, and IntegerPart is a function for
generating the greatest integer that does not exceed the argument
put in square brackets.
44. The autostereoscopic projection arrangement according to claim
42, in which at least two of the filter arrays cannot be made
completely congruent by horizontal and/or vertical linear scaling
of their structures, and the filter arrays are arranged at a
distance (z.sub.A) in front or behind the projection screen (in
viewing direction), respectively, in which (z.sub.A) may adopt
values in the range of -60 mm.ltoreq.(z.sub.A).ltoreq.60 mm, with a
negative value of (z.sub.A) meaning arrangement in front of the
projection screen and a positive value of (z.sub.A) meaning
arrangement behind the projection screen at the respective distance
given by the absolute amount of (z.sub.A).
45. The autostereoscopic projection arrangement according to claim
42, in which at least one filter element of at least one of the
filter arrays comprises a lens or a prism.
46. The autostereoscopic projection arrangement according to claim
45, in which the lens comprises a cylindrical lens.
47. The autostereoscopic projection arrangement according to claim
45 in which the lenses or prisms are arranged in columns only or in
rows only.
48. The autostereoscopic projection arrangement according to claim
42 in which the projection screen is translucent.
49. The autostereoscopic projection arrangement according to claim
42 in which at least one of the projectors projects a combination
image composed of bits of partial information of at least two views
(A.sub.k), in which preferably two projectors each project a
combination image composed of bits of partial information of at
least two views (A.sub.k) and the image combination structure of
the views (A.sub.k) selected differs for the said two
projectors.
50. The autostereoscopic projection arrangement according to claim
41, further comprising a second projector, in which the first
filter array is arranged between the projection screen and the
projectors, and in which the projection screen is suitable for
front projection; and in which the filter array has wavelength
filter elements that are arranged in columns and rows, are
transparent to light of different wavelengths or different
wavelength ranges, and absorb the light that is not transmitted at
least partially, and in which the projectors project bits of
partial information from views of a scene or object through at
least one of the first and second filter arrays and onto the
projection screen, so that bits of partial information of the views
are made optically visible on the projection screen in combination
or mix determined by a geometry of the arrangement, and the
projection screen is divided into a grid of image rendering
elements which are arranged in columns and rows and, depending on
the embodiment of the filter arrays and the projectors, radiate
light of particular wavelengths or wavelength ranges, with each
image rendering element rendering bits of partial information of at
least one of the views, and in which the first filter array defines
propagation directions for the light radiated by the projection
screen toward the observer, in which any individual image rendering
element corresponds with several allocated wavelength filters of
the filter array, or one wavelength filter of the filter array
corresponds with several allocated image rendering elements, in
such a way that a straight line connecting a first centroid of the
cross-section area of a visible portion of the image rendering
element and a second centroid of the cross-section area of a
visible portion of the wavelength filter represents one propagation
direction, so that, from every viewing position, the observer will
see predominantly bits of partial information of a first selection
of views with the first eye, and predominantly bits of partial
information of a second selection of views with the second eye, so
that the observer perceives a spatial impression from a multitude
of viewing positions.
51. The autostereoscopic projection arrangement according to claim
50, in which the filter array comprises wavelength filter elements
(.beta..sub.pq) in a grid of rows (q) and columns (p), which,
depending on their transmission wavelength/their transmission
wavelength range (.lamda..sub.b) are arranged on the filter array
according to the following function: b = p - d pq q - n m
IntegerPart [ p - d pq q - 1 n m ] , ##EQU12## wherein (p) is the
index of a wavelength filter .beta..sub.pq in a row of the array,
(q) is the index of a wavelength filter .beta..sub.pq in a column
of the array, (b) is an integer that defines one of the specified
transmission wavelengths/wavelength ranges (.lamda..sub.b) for a
wavelength filter (.beta..sub.pq) of the filter array in the
position (p,q), and may have values between 1 and b.sub.max,
(n.sub.m) is an integer greater than zero that preferably
corresponds to the total number (n) of the views (A.sub.k)
displayed by the projectors, (d.sub.pq) is a selectable mask
coefficient matrix for varying the arrangement of the wavelength
filters on the array, and IntegerPart is a function for generating
the greatest integer that does not exceed the argument put in
square brackets.
52. The autostereoscopic projection arrangement according to claim
50, in which the filter array is arranged on the projector side of
the projection screen at a distance (z), with (z) adopting values
in the range of 0 mm.ltoreq.z.ltoreq.60 mm.
53. The autostereoscopic projection arrangement according to claim
50, in which at least some of the filter elements of the filter
array transmit light from selected directions of incidence
only.
54. The autostereoscopic projection arrangement according to claim
41, in which: the projection screen is suitable for front
projection, the first filter array is arranged between the
projection screen and the projector, the first filter array
comprises wavelength filter elements that are arranged in columns
and rows, are transparent to light of different wavelengths or
different wavelength ranges, and absorb the light that is not
transmitted at least partially and in which the projector projects
bits of partial information from views of a scene or object through
at least one of the first and second filter arrays and onto the
projection screen, so that bits of partial information of the views
are made optically visible on the projection screen in combination
or mix determined by a geometry of the arrangement, and the
projection screen is divided into a grid of image rendering
elements which are arranged in columns and rows and, depending on
the embodiment of the filter arrays and the projectors, radiate
light of particular wavelengths or wavelength ranges, with each
image rendering element rendering bits of partial information of at
least one of the views, and in which the first filter array defines
propagation directions for the light radiated by the projection
screen toward the observer, in which any individual image rendering
element corresponds with several allocated wavelength filters of
the filter array, or one wavelength filter of the filter array
corresponds with several allocated image rendering elements, in
such a way that a straight line connecting a first centroid of the
cross-section area of a visible portion of the image rendering
element and a second centroid of the cross-section area of a
visible portion of the wavelength filter represents one propagation
direction, so that, from every viewing position, the observer will
see predominantly bits of partial information of a first selection
of views with the first eye, and predominantly bits of partial
information of a second selection of views with the second eye, so
that the observer perceives a spatial impression from a multitude
of viewing positions.
55. The autostereoscopic projection arrangement according to claim
41, in which: the projection screen is a translucent projection
screen, and further comprising a second filter array, in which the
first filter array is arranged between the projection screen and
the projectors, and the second filter array is arranged front of
the projection screen and in which the first and second filter
arrays have wavelength filter elements arranged in columns and rows
that are transparent to light of different wavelengths or different
wavelength ranges and in which the projector projects bits of
partial information from views of a scene or object through at
least one of the first and second filter arrays and onto the
projection screen, so that bits of partial information of the views
are made optically visible on the projection screen in combination
or mix determined by a geometry of the arrangement, and the
projection screen is divided into a grid of image rendering
elements which are arranged in columns and rows and, which radiate
light of particular wavelengths or wavelength ranges, with each
image rendering element rendering bits of partial information of at
least one of the views, and in which the second filter array,
arranged in front of the projection, screen defines propagation
directions for the light radiated by the projection screen toward
the observer, in which any individual image rendering element
corresponds with several allocated wavelength filters of the filter
array, or one wavelength filter of the filter array corresponds
with several allocated image rendering elements, in such a way that
a straight line connecting a first centroid of the cross-section
area of a visible portion of the image rendering element and a
second centroid of the cross-section area of a visible portion of
the wavelength filter represents one propagation direction, so
that, from every viewing position, the observer will see
predominantly bits of partial information of a first selection of
views with the first eye, and predominantly bits of partial
information of a second selection of views with the second eye, so
that the observer perceives a spatial impression from a multitude
of viewing positions.
56. The autostereoscopic projection arrangement according to claim
54, in which the projector radiates light of different wavelengths
or wavelength ranges in succession, and the bits of partial
information of each of the views are radiated in pairs of different
wavelengths or wavelength ranges, in which bits of partial
information of n=3 views (A.sub.k with k=1 . . . n) are displayed,
the projector is a DMD/DLP projector, and view A.sub.1 (k=1) is
displayed exclusively in red, view A.sub.2 (k=2) exclusively in
green, and view A.sub.3 (k=3) exclusively in blue.
57. The autostereoscopic projection arrangement according to claim
55, in which the projector radiates light of different wavelengths
or wavelength ranges in succession, and the bits of partial
information of each of the views are radiated in pairs of different
wavelengths or wavelength ranges, in which bits of partial
information of n=3 views (A.sub.k with k=1 . . . n) are displayed,
the projector is a DMD/DLP projector, and view A.sub.1 (k=1) is
displayed exclusively in red, view A.sub.2 (k=2) exclusively in
green, and view A.sub.3 (k=3) exclusively in blue.
58. Autostereoscopic projection arrangement according to claim 41,
in which: the projection screen is a translucent projection screen,
the first projector is arranged behind the projection screen, the
first filter array is arranged in front of the projection screen,
the first filter array has wavelength filter elements arranged in
columns and rows that are transparent to light of different
wavelengths or different wavelength ranges and in which the
projector projects bits of partial information from views of a
scene or object through at least one of the first and second filter
arrays and onto the projection screen, so that bits of partial
information of the views are made optically visible on the
projection screen in combination or mix determined by a geometry of
the arrangement, and the projection screen is divided into a grid
of image rendering elements which are arranged in columns and rows
and, which radiate light of particular wavelengths or wavelength
ranges, with each image rendering element rendering bits of partial
information of at least one of the views, and in which the second
filter array, arranged in front of the projection screen, defines
propagation directions for the light radiated by the projection
screen toward the observer, in which any individual image rendering
element corresponds with several allocated wavelength filters of
the filter array, or one wavelength filter of the filter array
corresponds with several allocated image rendering elements, in
such a way that a straight line connecting a first centroid of the
cross-section area of a visible portion of the image rendering
element and a second centroid of the cross-section area of a
visible portion of the wavelength filter represents one propagation
direction, so that, from every viewing position, the observer will
see predominantly bits of partial information of a first selection
of views with the first eye, and predominantly bits of partial
information of a second selection of views with the second eye, so
that the observer perceives a spatial impression from a multitude
of viewing positions.
59. Autostereoscopic projection arrangement according to claim 41,
in which the projected bits of partial information of the views are
projected together with the use of an image pre-rectification
function.
60. The autostereoscopic projection arrangement according to claim
42 in which the alignment and structure of the filter array between
the projectors and the projection screen are selected in such a way
that each image rendering element on the projection screen can
receive light from at least one of the projectors, and the
projection screen is curved, so that essentially equal angles of
incidence are obtained for the light received from the various
projectors.
61. The autostereoscopic projection arrangement according to claim
60, in which for each projector, a separate projection position and
projection direction is specified related to the projection screen,
preferably with the projection direction and the projection
distance differing from projector to projector.
62. The autostereoscopic projection arrangement according to claim
41, in which The brightness of the first projector is variable
within specified limits, and the first projector is selected from a
group consisting of slide projectors, DLP/DMD projectors, CRT
projectors and liquid crystal projectors.
63. The autostereoscopic projection arrangement according to claim
41, in which the filter array located nearest to the observer
comprises an antireflection coating.
64. The autostereoscopic projection arrangement according to claim
41, in which the filter array comprises an exposed film, a printed
pattern or an optical grating.
65. The autostereoscopic projection arrangement according to claim
42, in which at least one of the filter arrays is laminated onto a
substrate.
66. The autostereoscopic projection arrangement according to claim
42, in which at least one of the filter arrays is arranged within a
sandwich stack of several substrates, each substrate having
specified optical properties.
67. The autostereoscopic projection arrangement according to claim
41, in which the projection screen is designed as a very thin wafer
by which an excellent definition of the image rendering elements on
the projection screen is achieved.
68. The autostereoscopic projection arrangement according to claim
41, in which the projection screen has a light-concentrating
effect.
69. The autostereoscopic projection arrangement according to claim
1, in which parts of the filter array are provided with a
reflecting surface that is arranged on the side of the filter array
facing the projector.
70. The autostereoscopic projection arrangement according to claim
69, in which the reflecting surface is provided on non-transparent
filter elements only, so that part of the light projected is
reflected back into the projectors.
71. The autostereoscopic projection arrangement according to claim
41, in which at least some of the filter elements of the filter
arrays are polarizing filters, and the projector radiates polarized
light.
72. The autostereoscopic projection arrangement according to claim
71, in which the polarized light radiated by the first projector
alternates in time between horizontally linear and vertically
linear polarization.
73. The autostereoscopic projection arrangement according to claim
41, in which at least some of the filter elements of the filter
array are photochromic or electrochromic optical elements.
74. The autostereoscopic projection arrangement according to claim
42, in which the projectors comprise a color filter, such that
light radiated by the projectors can only pass wavelength filters
of a respective transmission wavelength range, and the projectors
are arranged in at least two substantially horizontal tiers, and
further comprising automatic alignment devices for the
projectors.
75. The autostereoscopic projection arrangement according to claim
41, in which the path of the light radiated by at least one
projector is folded by means of at least one mirror, with the
folded light path causing a light incidence on the projection
screen that is nonperpendicular relative to the main direction of
light propagation, and the projection screen comprises a
holographic disk that especially transmits and concentrates light
incident other than perpendicularly.
76. The autostereoscopic projection arrangement according to claim
41, in which at least some of the filter elements are designed as
neutral density filters for wavelength-independent attenuation of
light intensity.
77. An autostereoscopic projection arrangement, comprising: at
least one projector arranged for backprojection of bits of partial
image information from at least two views of a scene or object onto
a holographic screen, in which the holographic screen has a
multitude of holographic optical elements (HOEs) that are arranged
in a grid of columns and/or rows, and light incident from the
projector is optically imaged by an optical imaging system, onto
the holographic screen such that the multitude of HOEs define a
multitude of propagation directions, so that an observer will see
predominantly bits of partial information of a first selection of
views with one eye and predominantly bits of partial information of
a second selection of views with the other eye, and thus will
perceive a spatial impression from a multitude of viewing
positions.
78. The autostereoscopic projection arrangement according to claim
77, in which each HOE displays the light incident from the at least
one projector by at least one of the following optical imaging
types selected from a group consisting of: a) imaging by a lens, b)
imaging by a cylindrical lens arranged vertically or obliquely to
the vertical, c) diffusely transparent or translucent imaging, with
subsequent imaging by a lens, d) imaging by a prism, e) diffusely
transparent or translucent imaging, with subsequent imaging by
means of a prism, f) imaging through a polygonal polarizing filter
stepped neutral density filter wavelength filter or a combination
of the foregoing, with a wavelength filter transmitting light of a
specified wavelength or one or several specified wavelength ranges,
g) imaging by an optical flat, h) imaging by diffraction.
79. The autostereoscopic projection arrangement according to claim
78, comprising eight projectors, each of which renders one view of
the scene or object, and arranged on a circular arc, with the
imaging beam paths of the projectors being directed onto the rear
side of the holographic screen and the optical axes of these
imaging beam paths including angles of about
.alpha..apprxeq.8.6.degree., in which the HOEs are spaced from each
other on the holographic screen by approximately 0.1 mm in both
coordinates, and the propagation directions of the light radiated
by the holographic screen and carrying bits of partial information
of the views include angles of about .beta..apprxeq.0.83.degree.,
in which the multitude of viewing positions are established at a
distance of approximately 4.5 m from the holographic screen.
80. The autostereoscopic projection arrangement according to claim
78, comprising four projectors, each of which renders two views of
the scene or object, and arranged on a circular arc, with the
imaging beam paths of the projectors being directed onto the rear
side of the holographic screen and the optical axes of these
imaging beam paths including angles of about
.alpha..apprxeq.17.2.degree., in which the HOEs are spaced from
each other on the holographic screen by approximately 0.1 mm in
both coordinates, and the propagation directions of the light
radiated by the holographic screen and carrying bits of partial
information of the views include angles of about
.beta..apprxeq.17.2.degree., in which the multitude of viewing
positions are established at a distance of approximately 4.5 m from
the holographic screen.
81. The autostereoscopic projection arrangement according to claim
77 further comprising: at least one projector arranged for the
front-side projection of bits of partial image information from at
least two views of a scene or object onto a holographic screen, in
which each HOE displays the light incident from at least one
projector by at least one of the optical imaging types or
combinations of imaging types selected from a group consisting of:
a) imaging by a concave mirror, b) imaging by a convex mirror, c)
imaging by a cylindrical concave mirror arranged vertically or
obliquely to the vertical, d) diffuse reflection, with subsequent
imaging of a concave or convex mirror, preferably a cylindrical
concave mirror arranged vertically or obliquely to the vertical, e)
imaging by means of a doublet or triplet of corner reflector
mirrors, f) diffuse reflection, with subsequent imaging by means of
a doublet or triplet of mirrors, g) imaging through a polygonal
polarizing filter, a stepped neutral density filter, a wavelength
filter or a combination of the foregoing, with a wavelength filter
transmitting light of a specified wavelength or one or several
specified wavelength ranges, h) diffuse reflection, with subsequent
imaging by an optical flat, i) diffuse reflection, with subsequent
imaging by a prism, j) imaging by diffraction.
82. The autostereoscopic projection arrangement according to claim
77 in which at least two of the HOEs on the holographic screen
deviate from each other in their outer dimensions, their outer
shape, or both.
83. The autostereoscopic projection arrangement according to claim
77 in which the relative positions of area centroids of at least
two of the HOEs on the holographic screen deviate from each other
by an offset equal to a non-integral multiple of the width, height
of one of the said HOEs, or both.
84. The autostereoscopic projection arrangement according to claim
77, in which at least one of the HOE displays light of different
wavelength ranges in pairs of disjoint directions.
85. Autostereoscopic projection arrangement according to claim 77,
in which the grid in which the HOEs are arranged on the holographic
screen is an orthogonal grid.
86. The autostereoscopic projection arrangement according to claim
77, in which the grid in which the HOEs are arranged on the
holographic screen is a non-orthogonal grid, in which the rows
intersect the columns at an angle that is not equal to 90
degrees.
87. The autostereoscopic projection arrangement according to claim
77, in which at least one HOE simultaneously defines at least two
light propagation directions for light from at least one direction
of incidence.
88. The autostereoscopic projection arrangement according to claim
77, comprising at least two projectors, with each projector
projecting either bits of partial image information of only one
view of a scene or object, or simultaneously bits of partial image
information of at least two views of a scene or object, at least
one projector projects bits of partial image information of at
least one view of the scene or object at certain points in time
only, at a specified frequency between about 10 Hz and about 60 Hz,
the light of at least of one projector is displayed in such a way
that it can be seen from the front side within a solid angle that
is at least about 0.3.pi.*sr, so that the light of the said
projector is seen by the observer as an essentially two-dimensional
image, in which each of the projectors comprises at least one DMD
chip, one LCD component, one CRT or one laser.
89. The autostereoscopic projection arrangement according to claim
77, in which there is, in a viewing space, at least one viewing
position for an observer's eye into which the holographic screen
does not radiate essentially any of light projected by the
projectors.
90. The autostereoscopic projection arrangement according to claim
77, further comprising a color mask in a beam path between the
projector and the projection screen, the color mask directing
different color shares, the colors red, green and blue, to
different subpixels belonging to a pixel of the projection screen,
such that the subpixels, in addition to the pure colors red, green
and blue, also render mixed colors, so that a greater number of
colors per subpixel can be rendered and the resolution of the
projection screen is thus increased.
91. The autostereoscopic projection arrangement according to claim
90, characterized in that the width I.sub.new of the colors that
can be rendered per pixel results from l new = l .times. n 2
.times. n - 1 ##EQU13## wherein 1 is the size of one subpixel and n
the number of subpixels per pixel, or in that the number p.sub.new
of views renderable per pixel increases according to the function p
new = p .times. 2 .times. n - 1 n ##EQU14## wherein n is the number
of subpixels per pixel, and p the number of different views of the
scene or object.
92. The autostereoscopic projection arrangement according to claim
90, in which n=3 and p=8.
93. A method of manufacturing a holographic screen for use in an
autostereoscopic projection arrangement, comprising the steps of:
a) manufacturing a first optical arrangement containing a multitude
of the optical components permitting optical imaging types or
combinations of imaging types selected from a group consisting of:
imaging by a concave mirror, imaging by a convex mirror, imaging by
a cylindrical concave mirror arranged vertically or obliquely to
the vertical, diffuse reflection, with subsequent imaging of a
concave or convex mirror, preferably a cylindrical concave mirror
arranged vertically or obliquely to the vertical, imaging by means
of a doublet or triplet of corner reflector mirrors, diffuse
reflection, with subsequent imaging by means of a doublet or
triplet of mirrors, imaging through a polygonal polarizing filter,
a stepped neutral density filter, a wavelength filter or a
combination of the foregoing, with a wavelength filter transmitting
light of a specified wavelength or one or several specified
wavelength ranges, diffuse reflection, with subsequent imaging by
an optical flat, diffuse reflection, with subsequent imaging by a
prism, imaging by diffraction, imaging by a lens, imaging by a
cylindrical lens arranged vertically or obliquely to the vertical,
diffusely transparent or translucent imaging, with subsequent
imaging by a lens, imaging by a prism, diffusely transparent or
translucent imaging, with subsequent imaging by means of a prism,
imaging through a polygonal polarizing filter stepped neutral
density filter wavelength filter or a combination of the foregoing,
with a wavelength filter transmitting light of a specified
wavelength or one or several specified wavelength ranges, imaging
by an optical flat, b) positioning of an undeveloped holographic
screen in the vicinity of the first optical arrangement; c)
exposing the holographic screen to one or several coherent light
sources, in which the holographic screen is struck by a reference
beam coming directly from the light source and an object beam
which, also coming from the light source, has passed the first
optical arrangement. d) developing the holographic screen.
94. The method according to claim 93 further comprising the step of
repeating step "c" several times.
95. The method according to claim 93 further comprising the steps
of repositioning the light source relative to the optical
arrangement and repeating step "c".
96. The method according to claim 93 further comprising the steps
of substituting a second optical arrangement for the first optical
arrangement and repeating step "c".
97. A method of manufacturing a holographic screen for use in an
autostereoscopic projection arrangement, comprising the steps of:
a) selecting a multitude of optical components providing the
optical imaging types or combinations thereof, selected from a
group consisting of: imaging by a concave mirror, imaging by a
convex mirror, imaging by a cylindrical concave mirror arranged
vertically or obliquely to the vertical, diffuse reflection, with
subsequent imaging of a concave or convex mirror, preferably a
cylindrical concave mirror arranged vertically or obliquely to the
vertical, imaging by means of a doublet or triplet of corner
reflector mirrors, diffuse reflection, with subsequent imaging by
means of a doublet or triplet of mirrors, imaging through a
polygonal polarizing filter, a stepped neutral density filter, a
wavelength filter or a combination of the foregoing, with a
wavelength filter transmitting light of a specified wavelength or
one or several specified wavelength ranges, diffuse reflection,
with subsequent imaging by an optical flat, diffuse reflection,
with subsequent imaging by a prism, imaging by diffraction, imaging
by a lens, imaging by a cylindrical lens arranged vertically or
obliquely to the vertical, diffusely transparent or translucent
imaging, with subsequent imaging by a lens, imaging by a prism,
diffusely transparent or translucent imaging, with subsequent
imaging by means of a prism, imaging through a polygonal polarizing
filter stepped neutral density filter wavelength filter or a
combination of the foregoing, with a wavelength filter transmitting
light of a specified wavelength or one or several specified
wavelength ranges, imaging by an optical flat, b) arranging the
optical components in a grid of rows and/or columns; c) computing
respective holographic interference patterns for the imaging types
or combinations; d) exposing the holographic screen to one or
several coherent light sources such that the computed holographic
interference pattern is written onto the holographic screen; e)
developing the holographic screen.
Description
FIELD OF THE INVENTION
[0001] The invention relates to an autostereoscopic projection
arrangement comprising at least one projector, a projection screen
having a multitude of image rendering elements arranged in columns
and rows, and at least one filter array having a multitude of
filter elements arranged in columns and rows, in which the
projector or the projectors project bits of partial information
from views of a scene or object through one or several filter
arrays onto the projection screen so as to make these bits of
partial information visible on the image rendering elements.
DESCRIPTION OF PRIOR ART
[0002] An arrangement of this type is described, e.g., in DE 206
474. This patent specification discloses a projection screen having
a grid of lines each in front of and behind a ground glass screen
(in viewing direction). The grids contain narrow, vertical lines
which are alternatingly opaque and transparent, and through which
is a stereopair of images is back-projected. The observer or
observers looking through the grid in front see a spatial image, as
either of the viewer's eyes is offered a different perspective. The
drawback of this arrangement is that slight alignment errors of the
line grids or the ground glass screen may cause irritating effects
such as Moire patterns.
[0003] U.S. Pat. No. 5,146,246 describes a two-view projection. In
this arrangement, either of the observer's eyes is essentially
offered only one view, i.e. either the right or the left one. Here
again, a grid of lines each, i.e. a barrier screen, is arranged in
front of and behind the projection screen (in viewing direction).
This barrier screen is comprehensively disclosed as a pattern of
opaque and transparent vertical stripes. A similar arrangement
devised by the same inventor is described in U.S. Pat. No.
5,225,861. This is a back projection system, which projects a
left-hand and a right-hand image each through a grid of opaque and
transparent elements, in which, because of another grid of opaque
and transparent elements, the observer's eyes are presented
essentially disjoint views. This patent specification also
describes vertical opaque and transparent stripes as grid
elements.
[0004] For the two patent specifications mentioned last it is true
again that the arrangements described require a large scope of
alignment work. Moreover, the means of image separation described
in addition are essentially suitable only for systems showing two
views, so that the observer(s) of the stereoscopic image is/are
hardly given any freedom of movement.
[0005] Patent application JP 9179090 describes a back projection
system with a lenticular, in which at least two views of a scene
are presented in a time-multiplex mode. Allocation of the
back-projected views to the stripe segments on the projection
screen, which correspond to the imaging directions of the
lenticulars, is effected through controllable liquid crystal
segments. These segments are switched to be either transparent or
scattering, so that, depending on their respective states, a
particular view is imaged by means of the lenticulars in always one
or several defined directions. As a first disadvantage, this
arrangement involves a large equipment outlay. In particular, it
requires comprehensive control electronics. Moreover, despite the
views presented in a time-multiplex mode at full resolution, the
observer only sees one image per eye at a time, and at a reduced
horizontal resolution. For flicker-free rendition, the arrangement
further requires fast projection image display devices. The frame
repetition rate of these image display devices must be the higher,
the more views are to be presented, which adds to the cost of the
arrangements.
[0006] U.S. Pat. No. 4,101,210 and U.S. Pat. No. 4,132,468 describe
a stereo-projection for several views of a scene, in which, due to
the imaging means provided on a screen (e.g., an emulsion),
continuous, non-overlapping mosaic images with line structures are
formed of several views. These mosaic images have virtually no
gaps, i.e. their view portions are imaged quite next to each other.
The said imaging means comprise, in particular, the use of lens
arrays in combination with lenticulars.
[0007] DE 35 29 819 C2 describes a projection of several views
through a lenticular. In this arrangement, projection of the strips
of views to below each individual cylindrical lens is effected by
the respective neighboring cylindrical lenses. The advantage of
this is that the projector housings need not be particularly narrow
in order to achieve the correct combination of views on the
projection screen. The disadvantage is that, especially with large
screen diameters, lenticulars of large size are needed.
[0008] DE 1 96 08 305 A1 discloses a back projection system in
which two views are projected onto one screen through vertical
barrier stripes. The mosaic image resulting from the two views is
then made visible to the observer by a barrier screen in such a way
that the observer's eyes see different views, which produces a 3D
impression. The arrangement is characterized by a sliding
mechanism, which shifts the barrier screen on the observer's side
in accordance with the observer's eye position. One disadvantage of
this arrangement is that only two views of a scene are used;
another, that the control loop for ascertaining the eye position
and accordingly shifting the barrier screen on the observer's side
has a certain hysteresis, so that the observer sometimes sees a
pseudoscopic image. In common embodiments, the arrangement is only
suitable for a single observer.
[0009] DE 37 00 525 A1 describes a projection device with a
lenticular. The projection area in this arrangement is curved.
Among other disadvantages, the arrangement requires much space
where large-size screens are used.
[0010] WO 98/43441 A1 describes a dynamic multiple-view projection
system with shutters. The main disadvantage her is the extensive
work involved in manufacturing the arrangement.
[0011] U.S. Pat. No. 2,313,947 discloses a multiple-view projection
with two barrier screens comprising vertical barrier stripes. U.S.
Pat. No. 2,307,276 also describes a multiple-view projection with
barrier screens using vertical barrier stripes, in which,
characteristically, a certain stripe width between the view stripes
produced on the screen remains dark. This largely prevents
pseudoscopic and double-image positions.
[0012] U.S. Pat. No. 4,872,750 describes a back-projection system
with a barrier screen on the rear side, in which color images are
produced by an overlap between separate RGB projections. The
preferred means used here for spatial re-embodiment are
lenticulars. The comprehensive equipment involved is a
disadvantage.
[0013] Patent application DE 1 95 06 648 critically reviews, in the
context of prior art in 3D imaging, the sudden change in
perspective that occurs when the observer moves and that is due to
the discrete number of views presented. The authors describe an
autostereoscopic arrangement that avoids these disadvantages, and
in which several views are presented in observable zones so that
overlapping ranges are produced between the observation zones and
so that the illumination intensity of the various observation zones
is reduced at the margins. The optical imaging devices described
include, among others, aperture diaphragms which, in transition
regions, produce overlapping observation zones of two views each.
The principle on which this patent application is based call for a
considerable technical outlay if 3D images of larger size are
required.
[0014] In DE 100 03 326 C2, the present applicant describes
autostereoscopic methods and corresponding arrangements, in which
the spatial impression for several observers without personal
optical aids is produced by means of a wavelength filter array. The
filter array, which is located in front of or behind an image
display device, consists of a multitude of wavelength filters
arranged in rows and columns, which are transparent to light of
specified wavelengths or wavelength ranges and thus define discrete
wavelength-dependent light propagation directions for the light
emitted by the image display device. On the image display device,
with its image rendering elements arranged in rows and columns, an
image composed of several views of a scene or object is presented
so that, due to the filter array, the observer's two eyes will see
predominantly different selections of views. The disadvantage is
that large-image projectors cannot readily be implemented in this
way.
DESCRIPTION OF THE INVENTION
[0015] Proceeding from the prior art as described, it is the object
of the invention to improve arrangements of the type described
above in such a way that improved perception is achieved even with
images of larger size. Preferably, this object should be
accomplished by means of simple, or easily manufacturable,
components. It is another object of the invention to provide a
spatial impression to several observers at a time.
[0016] According to the invention, the object is accomplished by an
autostereoscopic projection arrangement, comprising: [0017] at
least one projector and [0018] at least one filter array having a
multitude of filter elements arranged in columns and rows, in which
[0019] by means of the projector/the projectors, bits of partial
information from views of a scene or object are projected onto a
projection screen, where these bits of partial information are
rendered on image rendering elements and, after passing one or
several of the filter arrays, are made visible to at least one
observer, and in which [0020] the image rendering elements
correspond with correlated filter elements, as regards the
propagation direction of the bits of partial information, in such a
way that an observer will see predominantly bits of partial
information from a first selection of views with one eye and
predominantly bits of partial information from a second selection
of views with the other eye, so that the observer gets a spatial
impression.
[0021] In a preferred embodiment of the invention, the
autostereoscopic projection arrangement comprises at least two
projectors, one projection screen, and at least two filter arrays
(F.sub.1, F.sub.2, . . . F.sub.A, . . . ), with at least one filter
array (F.sub.1) being arranged between the projection screen and
the at least two projectors, i.e. (in viewing direction) behind the
projection screen, and at least one filter array (F.sub.2) being
arranged (in viewing direction) in front of the projection screen,
and in which all filter arrays (F.sub.1, F.sub.2, . . . F.sub.A, .
. . ) have wavelength filter elements arranged in columns and rows,
which are transparent to light of different wavelengths (.lamda.)
or different wavelength regions (.DELTA..lamda.), and in which, by
means of the projectors, bits of partial information from n views
A.sub.k (with k=1 . . . n; n.gtoreq.2) of a scene or object are
projected onto projection screen through at least one filter array
(F.sub.1) so that bits of partial information from the views
(A.sub.k) are made visible on the projection screen in a
combination or mix determined by the geometry of the arrangement,
and in which the projection screen is divided into a grid of image
rendering elements (.alpha..sub.ij) of sufficient resolution
arranged in columns (i) and rows (j), which, depending on the
configurations of the filter arrays (F.sub.1, F.sub.2, . . .
F.sub.A, . . . ) and the projectors, deliver light of particular
wavelengths (.lamda.) or wavelength ranges, and in which each image
rendering element (.alpha..sub.ij) renders a bit, or bits, of
partial information from at least one of the views A.sub.k, and in
which propagation directions are defined for the light radiated
toward the observer by the projection screen through the at least
one filter array (F.sub.2), arranged (in viewing direction) in
front of the projection screen, so that each single image rendering
element (.alpha..sub.ij) corresponds with several correlated
wavelength filters of the filter array (F.sub.2), or each single
wavelength filter of the filter array (F.sub.2) corresponds with
several correlated image rendering elements (.alpha..sub.ij) in
such a way that the straight line connecting the centroid of the
cross-section area of a visible portion of the image rendering
element (.alpha..sub.ij) with the centroid of the cross-section
area of a visible portion of the wavelength filter corresponds to
one propagation direction, so that, from every viewing position, an
observer will see predominantly bits of partial information of a
first selection of views (A.sub.k) with one eye and predominantly
bits of partial information of a second selection of views
(A.sub.k) with the other eye, resulting in a spatial impression for
the observer from many viewing positions.
[0022] Preferably, a total number of 2, 4, 8, 16, 32 or 40
projectors can be used. Excellent spatial impressions, with good
brightness and convenient freedom of movement for several observers
are obtained with about 8 or more views presented, with preferably
8 or more projectors being used for projecting the views.
[0023] Preferably, the arrangement described above uses exactly two
filter arrays, (F.sub.1) and (F.sub.2). Special configurations in
which more than two filter arrays are of advantage are described
below. The wavelength filter elements contained in the wavelength
filter arrays may be transparent, e.g., for red, green, blue,
yellow, cyan or magenta and/or transparent or opaque for the total
visible wavelength range.
[0024] Further, the filter elements of the filter arrays (F.sub.1,
F.sub.2, . . . F.sub.A, . . . ) have shapes of any, preferably
polygonal, and particularly preferably rectangular outline. As a
rule, a filter element has a surface area of approximately a few
10,000 .mu.m.sup.2 up to several mm.sup.2. Deviations from that
range are possible in particular cases. The shape and/or size of
the filter element may vary within a filter array or even within a
row or column of a filter array. The shape of the image rendering
elements on the projection screen essentially depends on the filter
arrays on the projector side, so that the said variations in the
shape and/or size of the filter elements have an essential
influence on the image rendering elements.
[0025] The image produced on the projection screen, which is
composed of different bits of partial information from the views
(A.sub.k), shows a grid of image rendering elements
(.alpha..sub.ij) in columns (i) and rows (j), varying with the
structure of the filter array(s) and the geometric arrangement of
the projectors. This grid structure is not necessarily visible. The
image rendering elements (.alpha..sub.ij) may radiate light of
quite different wavelength ranges, depending on the kind of light
incident from the projector at the respective locations of the
projection screen. Depending on the embodiment of the invention,
there may be minor partial areas among the image rendering elements
of the projection screen that remain without any partial
information from any view (A.sub.k) because, e.g., no light from
any projector arrives at these partial areas. Such areas are not
necessarily to be considered as image rendering elements
(.alpha..sub.ij) in the grid (i,j). Although such arrangements also
lead to the desired result, they are not necessarily
preferable.
[0026] It is also feasible that one image rendering element
(.alpha..sub.ij) renders fully colored bits of partial image
information, which especially result from an optical mix of bits of
partial information from different wavelengths/wavelength ranges.
Moreover, also depending on the structure of the arrangement, such
an image rendering element may simultaneously render bits of
partial information from different image rendering element
positions within a view or even from different views, if, for
example, the light rays coming from two or several projectors
superimpose on the projection screen.
[0027] It is of advantage if each of the filter arrays (F.sub.1,
F.sub.2, . . . F.sub.A, . . . ) contains wavelength filter elements
(.beta..sub.Apq) in a separate matrix of rows (q.sub.A) and columns
(p.sub.A) assigned to the respective filter array, these rows and
columns being arranged on the filter array, depending on their
transmission wavelength or their transmission wavelength range
(.lamda..sub.Ab), according to the following function: b = p A - d
Apq q A - n Am IntegerPart .function. [ p A - d Apq q A - 1 n Am ]
, ##EQU1## [0028] A being the index of the respective array
(F.sub.A), [0029] (p.sub.A) the index of one wavelength filter
(.beta..sub.Apq) in a row of the respective array (F.sub.A), [0030]
(q.sub.A) the index of one wavelength filter (.beta..sub.Apq) in a
column of the respective array (F.sub.A), [0031] (b) an integral
number that specifies one of the intended transmission
wavelengths/transmission wavelength ranges (.lamda..sub.Ab) for a
wavelength filter (.beta..sub.Apq) of the filter array (F.sub.A) in
the position (p.sub.A,q.sub.A) and which may adopt values between 1
and b.sub.Amax, [0032] (n.sub.Am) an integral value greater than
zero that preferably corresponds to the total number (n) of the
views (A.sub.k) projected by the projectors, [0033] (d.sub.Apq) a
selectable mask coefficient matrix for varying the arrangement of
wavelength filters on the respective array (F.sub.A), and [0034]
IntegerPart a function for generating the greatest integer not
exceeding the argument put in square brackets.
[0035] The entries in matrix (d.sub.Apq) may be real numbers, with
(p.sub.A) in the above equation corresponding to index (p), and
(q.sub.A) to index (q) for the matrix (d.sub.Apq) or for the filter
elements (.beta..sub.Apq).
[0036] It is also possible to specify, for different values of (b),
transmission wavelengths/transmission wavelength ranges
(.lamda..sub.Ab) of identical contents: If, e.g., b.sub.Amax=8,
.lamda..sub.A1 to .lamda..sub.A3 may stand for R,G,B in this order,
and .lamda..sub.A4 to .lamda..sub.A8 for wavelengths outside the
visible light region, in which case .lamda..sub.A1 to
.lamda..sub.A3 transmit the colors R,G,B, and .lamda..sub.A4 to
.lamda..sub.A8 block the visible spectrum. The combination rule for
a Filter (F.sub.A) with the index (A) and for the parameters
d.sub.Apq=-1=const and n.sub.Am=8, then, supplies a filter
structure that periodically generates oblique stripes in the RGB
colors on an opaque background. Between every two of these colored
stripes, five of the filter elements in every row remain opaque.
The angle of inclination of the colored stripes depends on the
dimensions of the filter elements (.beta..sub.Apq) In preferable
embodiments of the invention, b.sub.Amax and n.sub.Am are of equal
size.
[0037] In another exemplary embodiment, again several of the
transmission wavelengths/wavelength ranges .lamda..sub.Ab may have
identical filter actions: If .lamda..sub.A1 . . . .lamda..sub.A6
are wavelength ranges blocking the entire visible spectrum,
.lamda..sub.A7 and .lamda..sub.A8 filter ranges transparent to the
visible spectrum, and if n.sub.Am=8 and d.sub.Apq=-1=const, there
results, from the rule for generating a filter structure, an
essentially opaque filter array (F.sub.A), which contains oblique,
stepped transparent stripes equally distributed over the area and
occupying about one quarter of it.
[0038] It is further advantageous in that connection if at least
two of the filter arrays (F.sub.1, F.sub.2, . . . F.sub.A, . . . )
cannot be made to be completely congruent by horizontal and/or
vertical linear scaling of their structures. In other words, the
structures of the respective filter arrays do not turn into each
other by one- or two-dimensional magnification or demagnification.
With regard to the spatial impression, this lack of congruence has
the effect that the eye of an observer will, from actually every
viewpoint, always see a mix of bits of partial information from
several views (A.sub.k). This completely excludes the case that an
observer's eye in any position sees bits of partial information
from exactly one of the views (A.sub.k).
[0039] Moreover, such properties of the filter arrays have a
special effect: Suitable geometric arrangements provided, the
structure of a 2D view predominantly seen with one eye may change
while the observer moves. It is feasible, e.g., that 90% of the
image seen by an observer's eye in a particular position of the
observation space consists of bits of partial information from view
A.sub.1 (k=1), whereas the residual 10% is a mix of bits of partial
information from other views (A.sub.k) with k>1, with the bits
of partial information seen from view A.sub.1 (k=1) having a
resolution of, e.g., 600.times.400 pixels. Under the conditions
mentioned above, the structure of this predominantly seen view
A.sub.1 (k=1) may change in another viewing position so as to have
a visible resolution of, e.g., 400.times.600.
[0040] Sometimes the filter arrangement can be selected so that the
visible resolution per view differs from that of a single
projector.
[0041] For some applications it may further be of advantage if at
least part of the filter elements of at least one of the filter
arrays (F.sub.1, F.sub.2, . . . F.sub.A, . . . ) are configured as
neutral filters for the wavelength-independent attenuation of the
light intensity. For example, such filter elements may transmit 0%
(opaque), 25%, 50%, 75% or 100% (fully transparent) of the visible
light, irrespective of its wavelength. Such neutral filter elements
or stepped neutral density filter elements may be easier and
cheaper to make than colored wavelength filter array elements.
Moreover, it is possible, by means of a filter array with neutral
filter elements, to produce special effects, such as, for example,
the variation of the perceived light intensity of or several views
as the observer moves.
[0042] The filter arrays (F.sub.1, F.sub.2, . . . F.sub.A, . . . )
are arranged at a distance (z.sub.A) (in viewing direction) before
or behind the projection screen. (z.sub.A) adopts values within a
range of -60 mm.ltoreq.z.sub.A.ltoreq.+60 mm, with a negative value
of (z.sub.A) means arrangement (in viewing direction) in front of
the projection screen, and a positive value for (z.sub.A) means
arrangement (in viewing direction) behind the projection screen at
the distance of the absolute value of (z.sub.A). In exceptional
cases, the absolute amount (z.sub.A) may even have greater values
than 60 mm, for example, if the diagonal of the projection screen
is extremely large.
[0043] In another particular embodiment, part of the filter
elements of at least one of the filter arrays (F.sub.1, F.sub.2, .
. . F.sub.A, . . . ), preferably the one that is next to
observer(s), is designed in such a way that the said filter
elements transmit light of selected directions of incidence only.
This can be ensured, e.g., by the use of certain crystals or a
polymer coating.
[0044] Further it is feasible to design at least one filter element
of at least one of the filter arrays (F.sub.1, F.sub.2, . . .
F.sub.A, . . . ) as a lens, preferably a cylindrical lens, or as a
prism; the cylindrical lenses or prisms may be arranged in columns
only or rows only. In this way, a comparatively high light
transmission is achieved. Such embodiments are of interest
especially with regard to systems presenting significantly more
than eight views.
[0045] Whereas in simple embodiments of the invention each
projector projects bits of partial information of a single view
(A.sub.k) only, e.g. the respective 2D perspective view of the
scene to be imaged, it may be of advantage for the purposes of the
invention if at least one of the two or more projectors projects a
combination image composed of bits of partial information of at
least two views (A.sub.k). As an extension of this feature, it is
sometimes advantageous if (at least) two projectors each project a
combination image composed of bits of partial information of at
least two views (A.sub.k), and if the views (A.sub.k) for the said
two projectors have different image combination structures.
[0046] Regarding the combination of bits of partial information of
several views, reference is made to the applicant's patent
specification DE 1 00 03 326 C2 quoted above, in which a rule for
general image combination is given that is similar in kind to the
rule used herein for structuring the filter arrays.
[0047] In some embodiments of the invention, e.g. if at least one
of the projectors is directed at the projection screen under a
certain angle, the bits of partial information of the views can be
projected using a suitable image pre-rectification function, e.g. a
trapezoidal correction. In this connection, modern projectors
already offer continuous Scheimpflug and/or Seagull correction
functions which apply geometrical corrections to the projected
image. If transparencies are used as projection data, these can
also be made with a corresponding precorrection.
[0048] The arrangement according to the invention is particularly
efficient with regard to light and area utilization if the
structure of the filter array(s) and its/their alignment between
the projectors and the projection screen are selected in such a way
that each area element on projection screen can receive light from
at least one of the projectors. In that way, no "permanently black
areas" will result on the screen, so that each area element of the
projection screen presents a bit of partial information of at least
one view (A.sub.k). As mentioned above, however, this advantageous
embodiment is mandatory condition for maintaining the mode of
operation of the arrangements according to the invention.
[0049] The projection screen is preferably translucent. In addition
it may have a light-concentrating effect, i.e. have a positive
gain. Translucent and light-concentrating projection screens are
well known and need not be explained to those skilled in the art.
Excellent definition of the image rendering elements on the
projection screen is achieved if the projection screen is designed
as a very thin wafer, preferably with a thickness of less than one
millimeter.
[0050] In many embodiments of the invention, the projection screen
will be a flat wafer. Under special conditions, though, it may be
advantageous for the projection screen to be curved. In that case
it is recommendable that the filter arrays are provided with a
corresponding curvature.
[0051] For every projector, in general, a separate projection
position and a separate projection direction relative to the
projection screen are specified; preferably, the projection
directions and projection distances differ from projector to
projector. In conjunction with a curved projection screen, the
result is, e.g., that the light from the various projectors strikes
the projection screen essentially under the same angle of
incidence. Herein, the term "angle of incidence" describes the
angle under which the principal direction of light propagation of a
projected image is incident to the projection screen.
[0052] If all projector lenses are positioned at the same height
behind the projection screen, this height should preferably be
approximately that of the center point of the projection screen
surface. To ensure this positioning, one can use, e.g., a suitably
dimensioned mechanical stand.
[0053] The brightness of one or several projectors may sometimes be
variable within specified limits. This property, which is a feature
of some modern projectors, can be used here to ensure uniform
illumination of the projection screen. If, e.g., one of the views
of a scene should be somewhat brighter than the others because of
the taking conditions, brightness control of the respective
projector provides sufficient compensation.
[0054] Eligible projectors are, e.g., liquid crystal projectors,
DLP/DMD projectors, CRT projectors or slide projectors. Also
feasible is laser projection with, e.g., three lasers as separate
RGB image display devices. Of course, more than three lasers may be
used as well. The above enumeration of eligible projector types is
open to additions and is not meant to exclude arrangements
according to the invention using other projector types. Besides,
arrangements according to the invention may incorporate projectors
of different types simultaneously. The projectors may differ with
regard to their light modulation principle and/or individual
parameters, such as, e.g., light flux or image resolution.
[0055] As a rule, the projectors are furnished with image data by
an electronic control system, which may comprise one or several
separate units. In this connection it is also feasible to use an
image data source consisting of one video recorder per projector.
Each video recorder feeds the image sequence of one view (A.sub.k)
to the correlated projector. The video recorders are coupled to
each other via a trigger, so that all n views (A.sub.k) can be
displayed in synchronism.
[0056] It is further feasible to control each projector via a
separate computer, with all computers being synchronized, e.g., by
networking. The use of computers permits, in particular, an
embodiment in which at least one projector projects bits of partial
information from at least two different views (A.sub.k). With
regard to the possible combination of bits of partial information
from at least two different views (A.sub.k), reference is made
again to the patent specification DE 100 03 326 C2. Further,
commercial image signal-splitting computers can be used for
triggering several projectors simultaneously.
[0057] For image contrast enhancement, the filter array arranged
most closely to the observer may be provided with an antireflective
coating. This avoids reflections of extraneous light and further
improves the perception of the spatial image.
[0058] Each of the filter arrays (F.sub.1, F.sub.2, . . . F.sub.A,
. . . ) is designed, e.g., as an exposed film, a printed image or
an optical grating. Other ways of preparation are also feasible.
Preferably, at least one of the filter arrays (F.sub.1, F.sub.2, .
. . F.sub.A, . . . ) is laminated to a substrate, e.g., of glass.
This will provide good mechanical fixation. In another embodiment,
at least one of the filter arrays (F.sub.1, F.sub.2, . . . F.sub.A,
. . . ) is arranged within a sandwich structure consisting of
several substrates, with the substrates optionally having certain
optical properties, such as specified refractive indices. The
sandwich structure also provides good mechanical fixation, together
with a long service life of the filter arrays.
[0059] In a very special embodiment of the invention, parts of at
least one filter array are provided with a reflecting surface,
which is arranged on the side(s) of the filter array(s) facing the
projectors, and preferably only on the non-transparent filter
elements, so that part of the light projected is reflected back
into the projectors. If the respective projector is capable of
re-using such light ("transflective projection"), a higher degree
of light utilization can be achieved.
[0060] In further embodiments of the invention, at least some of
the filter elements of at least one of the filter arrays (F.sub.1,
F.sub.2, . . . F.sub.A, . . . ) are polarizing filters, and at
least one of the projectors radiates polarized light. The
polarizing filters may, e.g., be transparent for horizontally or
vertically linearly polarized light and at the same time,
optionally, be transparent only to light of particular
wavelengths/wavelength ranges. It is also feasible in that
connection to have a combination of wavelength-independent neutral
filters and polarizing filter properties. The
polarization-dependent transmission filters will pass the light of
those projectors only that have matching polarizing properties.
[0061] In another embodiment, at least one projector that radiates
polarized light emits the light in temporally alternating
polarization forms, preferably alternating between horizontally
linear and vertically linear polarization. This results in a
temporal change of the structure of the combination image formed on
the projection screen.
[0062] Further, at least part of the filter elements of at least
one of the filter arrays (F.sub.1, F.sub.2, . . . F.sub.A, . . . )
may generally be configured as photochromic or electrochromic
optical elements. In this way, a switching between 2D and 3D
projection can be effected, if the photochromic or electrochromic
elements permit, in a first state, the specified
wavelength/wavelength range transmission so as to create a spatial
impression ("3D mode"), whereas they are, in a second state,
largely transparent for practically the entire visible wavelength
spectrum. In the latter state, projection onto the projection
screen is almost uninfluenced by the said filter elements. If all
filter elements of all existing filter arrays are brought into that
state, it is possible for the observer(s) to have a practically
fully resolved 2D perception. Whereas in the 3D mode the projectors
project at least bits of partial information of two views, the 2D
mode projects exactly one view. In the simplest case, only one
projector projects one view in the common way, possibly also with
image rectifying correction. To improve brightness in the 2D mode,
several projectors may project on and the same image onto the
screen. In this case care should be taken to ensure that the
projectors project the images in such a way that all identical
views are superimposed on the screen in perfect registration.
[0063] It is just as well possible to use optical elements other
than photochromic or electrochromic ones. For switching between a
2D and a 3D mode in an embodiment of the invention, it is decisive
and essential that the optical elements, in a first state, transmit
defined wavelengths/wavelength ranges n or have defined
transmittances for the wavelength-independent attenuation of the
light intensity, whereas, in a second state, they have the highest
possible transmittance to essentially the full visible wavelength
spectrum.
[0064] In a particularly simple case which does not require any
electrochromic filter array elements, the filter arrays are simply
designed to be removable from the arrangement according to the
invention, to achieve a 2D projection.
[0065] In another embodiment of the arrangements according to the
invention, at least one of the projectors is provided with a color
filter, so that the light projected by the said projector can only
penetrate wavelength filters of the respective transmission
wavelength or the respective transmission wavelength range. In this
way it is possible to achieve particular combination structures of
the bits of partial information on the projection screen. For
special applications it will then also be possible for a moving
observer to perceive a color change of the views seen.
[0066] Instead of providing one or several projectors with color
filters it is also possible to use, e.g., DMD projectors, which
alternatingly project the red, green and blue partial images of a
full-color image. As this alternation is functionally inherent in
such a projector, no color filter is required.
[0067] Moreover, in other special embodiments of the invention, the
projectors may be arranged in at least two-essentially
horizontal-tiers. This has two advantages: On is that the structure
of the combination image formed on the projection screen can be
influenced. The other is that, if two projectors whose lenses are
arranged essentially one above the other project the same image,
the brightness of certain views, or parts of views, in the
combination image formed on the projection screen, can be
increased. It is also feasible to provide for a spatial offset
between the two tiers, e.g., in order to horizontally arrange the
projection lenses approximately at an observer's interpupillary
distance although the projector housings are distinctly broader
than the distance between a pair of human eyes.
[0068] For easy handling, the arrangement may optionally have means
for automatically aligning the projectors, e.g., via
electromechanical control elements. The projectors will then be
brought to a specified position after or during the process of
switching on.
[0069] Synchronization of the projectors may just as well be
effected manually as required. Preferably, this can be done by
means of projected test images featuring reference marks that can
be aligned with each other.
[0070] Further, the beam path of the light projected by at least
one projector may be folded by the provision of at least one
mirror. Such folding is common in prior art especially for the
purpose of saving space in optical assemblies. In the present case,
such folding has an additional favorable effect: The folded beam
path strikes the projection screen at an angle that is not
perpendicular relative to the main propagation direction of the
light. If the projection screen is designed as a holographic disk
that, in transmitting, concentrates especially light that is not
incident perpendicularly (such as, e.g., the product "HOPS" of
Sax3D GmbH, Chemnitz/Germany), a brilliant and high-contrast 3D
image is achieved even with ambient daylight.
[0071] As mentioned at the beginning, more than two filter arrays
(F.sub.1, F.sub.2, . . . F.sub.A, . . . ) may be used. It is of
advantage then to use three filter arrays, two of which are
preferably arranged between the projection screen and the
projectors, and one between the projection screen and the
observers. In this case, the light projected by the projectors
passes two filter arrays so that it gets particularly well
structured before it strikes the projection screen. In other
embodiment versions, more than three filter arrays may be used.
[0072] The object of the invention is also accomplished with the
following embodiment version of an autostereoscopic projection
arrangement, in this case by a 3D front projection arrangement.
This comprises [0073] at least two projectors, [0074] one
projection screen suitable for front projection, [0075] one filter
array arranged between the projection screen and the at least two
projectors, in which [0076] the filter array has wavelength filter
elements arranged in columns and rows, which are transparent to
light of different wavelengths (.lamda.) or different wavelength
regions (.DELTA..lamda.) and which absorb at least some, but
preferably a high proportion, of the non-transmitted light, and in
which [0077] the projectors project bits of partial information of
n views (A.sub.k with k=1 . . . n; n.gtoreq.2) of a the scene or
object through the filter array onto the projection screen, so that
the projection screen displays bits of partial information of the
views (A.sub.k) in a combination or mix defined by the geometry of
the arrangement, with the projection screen being divided into a
grid of image rendering elements (.alpha..sub.ij) of sufficient
resolution arranged in columns (i) and rows (j), which, depending
on the embodiment of the filter array and the projectors, deliver
light of particular wavelengths (.lamda.) or wavelength ranges, and
with each image rendering element (.alpha..sub.ij) rendering bit(s)
of partial information of at least one of the views (A.sub.k), and
in which [0078] the filter array defines propagation directions for
the light delivered by the projection screen towards the observer
on the projector side, with every one image rendering element
(.alpha..sub.ij) corresponding to several wavelength filters
correlated to it, and each wavelength filter of the filter array
corresponding to several image rendering elements (.alpha..sub.ij)
correlated to it, in such a way that the straight line connecting
the centroid of the cross-section area of a visible segment of the
image rendering element (.alpha..sub.ij) and the centroid of the
cross-section area of a visible segment of the wavelength filter
corresponds to one propagation direction, so that, from every
viewing position, an observer will see predominantly bits of
partial information of a first selection of views (A.sub.k) with
one eye and predominantly bits of partial information of a second
selection of views (A.sub.k) with the other eye and thus will have
a spatial impression from a great number of viewing positions.
[0079] In such a 3D front projection, the observer(s) is/are on the
projector side, but should, as a rule, be positioned where they do
not obstruct any of the projection beam paths.
[0080] In this embodiment, too, the wavelength filter elements
contained in the wavelength filter arrays may be transparent to,
e.g., red, green, blue, yellow, cyan or magenta, and/or transparent
or opaque to the total visible wavelength range.
[0081] The image formed on the projection screen as a combination
of different bits of partial information of the views (A.sub.k) has
a grid of image rendering elements (.alpha..sub.ij) in columns (i)
and rows (j) that varies with the structure of the filter array and
the geometric arrangement of the projectors. This grid is not
necessarily visible. The image rendering elements (.alpha..sub.ij)
may deliver light of different wavelength ranges, depending on the
light arriving from the projectors in the respective positions of
the projection screen. It is also feasible that an image rendering
element renders a full-color bit of partial information, which
especially originates from an optical mix of bits of partial
information from different wavelengths/wavelength ranges. Moreover,
also depending on the structure of the arrangement, such an image
rendering element may render bits of partial information from
different image rendering element positions within a view (A.sub.k)
or even from different views (A.sub.k).
[0082] Further, it is of advantage if the filter array contains
wavelength filter elements (.beta..sub.pq) in a grid of rows (q)
and columns (p), which, depending on their transmission
wavelength/transmission wavelength range (.lamda..sub.b), are
arranged on the filter array according to the following function: b
= p - d pq q - n m IntegerPart .function. [ p - d pq q - 1 n m ] ,
##EQU2## [0083] (p) is the index of one wavelength filter s
(.beta..sub.pq) in a row of the array, [0084] (q) is the index of
one wavelength filter (.beta..sub.pq) in a column of the array,
[0085] (b) is an integral number that specifies one of the intended
transmission wavelengths/transmission wavelength ranges
(.lamda..sub.b) for a wavelength filter (.beta..sub.pq) of the
filter array in the position (p,q) and which may adopt values
between 1 and b.sub.max, [0086] (n.sub.m) is an integral value
greater than zero that preferably corresponds to the total number n
of the views (A.sub.k) projected by the projectors, [0087]
(d.sub.pq) is a selectable mask coefficient matrix for varying the
arrangement of the wavelength filters on the array, and [0088]
IntegerPart is a function for generating the largest integral
number that does not exceed the argument put in square
brackets.
[0089] The filter elements of the filter array have any, preferably
polygonal, more preferably rectangular, outlines. In special
embodiments also of this front projection version, several filter
arrays (F.sub.A) can be used between den projectors and the
projection screen; the following description assumes only one
filter array, though.
[0090] For some applications it may be of advantage if at least
part of the filter elements are designed as neutral density filters
for the wavelength-independent attenuation of the light intensity.
Such neutral density filter elements or stepped neutral density
filter elements can sometimes be fabricated more economically than
wavelength filter array elements. In addition it is possible, by
means of a filter array with neutral density filter elements, to
produce special effects, such as the variation of the light
intensity of one or several views perceived by a moving
observer.
[0091] The filter array is arranged at a distance (z) (in viewing
direction) in front of the projection screen, i.e. on the observer
and projector sides, with (z) having an order of magnitude of 0
mm.ltoreq.z.ltoreq.60 mm. In exceptional cases, (z) may even be
bigger, e.g., if the diagonal of the projection screen is extremely
long.
[0092] In this embodiment, the projection screen will be a flat
plate, as a rule. It is feasible, though, to have a projection
screen that is not a plane but has a spatial structure; for
example, a cylindrical-periodical, reflecting surface is of
advantage in conjunction with front projection, because the very
structure of the projection screen will produce a certain pattern
of directions of the reflected light.
[0093] In another special embodiment, part of the filter elements
are designed to transmit light of selected directions of incidence
only. This can be effected, e.g., by the use of certain crystals or
a polymer coating. Furthermore it is feasible to design at least
one filter element as a lens, preferably a cylindrical lens, or as
a prism, such cylindrical lenses or prisms being possibly arranged
in columns only or rows only. In this way, a comparatively high
light transmission is achieved. Such embodiments are of special
interest in conjunction with systems displaying significantly more
than eight views.
[0094] The object of the invention is also accomplished with an
autostereoscopic projection arrangement comprising: [0095] a
projector, [0096] a projection screen suitable for front
projection, [0097] a filter array arranged between the projection
screen and the projector, in which [0098] the filter array has
wavelength filter elements arranged in columns and rows, which are
transparent to light of different wavelengths (.lamda.) or
different wavelength regions (.DELTA..lamda.) and which absorb at
least some, but preferably a high proportion, of the
non-transmitted light, and in which [0099] the projector projects
bits of partial information of n views (A.sub.k with k=1 . . . n;
n.gtoreq.2) of a the scene or object through the filter array onto
the projection screen, so that the projection screen displays bits
of partial information of the views (A.sub.k) in a combination or
mix defined by the geometry of the arrangement, with the projection
screen being divided into a grid of image rendering elements
(.alpha..sub.ij) of sufficient resolution arranged in columns (i)
and rows (j), which, depending on the embodiment of the filter
array and the projector, deliver light of particular wavelengths
(.lamda.) or wavelength ranges, and with each image rendering
element (.alpha..sub.ij) rendering bit(s) of partial information of
at least one of the views (A.sub.k), and in which [0100] the filter
array defines propagation directions for the light delivered by the
projection screen towards the observer on the projector side, with
every one image rendering element (.alpha..sub.ij) corresponding to
several wavelength filters correlated to it, and each wavelength
filter of the filter array corresponding to several image rendering
elements (.alpha..sub.ij) correlated to it, in such a way that the
straight line connecting the centroid of the cross-section area of
a visible segment of the image rendering element (.alpha..sub.ij)
and the centroid of the cross-section area of a visible segment of
the wavelength filter corresponds to one propagation direction, so
that, from every viewing position, an observer will see
predominantly bits of partial information of a first selection of
views (A.sub.k) with one eye and predominantly bits of partial
information of a second selection of views (A.sub.k) with the other
eye and thus will have a spatial impression from a great number of
viewing positions.
[0101] The object of the invention is also accomplished with the
following autostereoscopic projection arrangement, comprising:
[0102] a projector, [0103] a translucent projection screen, [0104]
at least two filter arrays (F.sub.1, F.sub.2, . . . F.sub.A, . . .
), with at least one filter array (F.sub.1) being arranged between
the projection screen and the projector, i.e. (in viewing
direction) behind the projection screen, and at least one filter
array (F.sub.2) being arranged (in viewing direction) in front of
the projection screen, in which [0105] all filter arrays (F.sub.1,
F.sub.2, . . . F.sub.A, . . . ) have wavelength filter elements
arranged in columns and rows, which are transparent to light of
different wavelengths (.lamda.) or different wavelength regions
(.DELTA..lamda.), and in which [0106] the projector projects bits
of partial information of n views (A.sub.k with k=1 . . . n;
n.gtoreq.2) of a the scene or object through at least one filter
array (F.sub.1) onto the projection screen, so that the projection
screen displays bits of partial information of the views (A.sub.k)
in a combination or mix defined by the geometry of the arrangement,
with the projection screen being divided into a grid of image
rendering elements (.alpha..sub.ij) of sufficient resolution
arranged in columns (i) and rows (j), which, depending on the
embodiment of the filter arrays (F.sub.1, F.sub.2, . . . F.sub.A, .
. . ) and the projector, deliver light of particular wavelengths
(.lamda.) or wavelength ranges, and with each image rendering
element (.alpha..sub.ij) rendering bit(s) of partial information of
at least one of the views (A.sub.k), and in which [0107] the at
least one filter array (F.sub.2), arranged (in viewing direction)
in front of the projection screen, defines propagation directions
for the light delivered by the projection screen towards the
observer, with every one image rendering element (.alpha..sub.ij)
corresponding to several wavelength filters of the filter array
(F.sub.2), and each wavelength filter of the filter array (F.sub.2)
corresponding to several image rendering elements (.alpha..sub.ij)
correlated to it, in such a way that the straight line connecting
the centroid of the cross-section area of a visible segment of the
image rendering element (.alpha..sub.ij) and the centroid of the
cross-section area of a visible segment of the wavelength filter
corresponds to one propagation direction, so that, from every
viewing position, an observer will see predominantly bits of
partial information of a first selection of views (A.sub.k) with
one eye and predominantly bits of partial information of a second
selection of views (A.sub.k) with the other eye and thus will have
a spatial impression from a great number of viewing positions.
[0108] In the two embodiment versions of the autostereoscopic
projection arrangements described above, which have only one
projector, the projector delivers, preferably in temporal
succession, light of different wavelengths or wavelength ranges.
Moreover, the bits of partial information of each of the n views
A.sub.k (with k=1 . . . n) are projected in pairs of different
wavelengths or wavelength ranges.
[0109] This approach can be implemented, e.g., by displaying bits
of partial information of n=3 views A.sub.k with a DMD/DLP
projector so as to display view A.sub.1 (k=1) exclusively in red,
view A.sub.2 (k=2) exclusively in green, and view A.sub.3 (k=3)
exclusively in blue. The color assignments can, of course, be
permutated and are not restricted to the assignment given here. As
a result, views of different color are made visible to the
observer(s).
[0110] The object of the invention is also accomplished with an
autostereoscopic projection arrangement, comprising: [0111] a
translucent projection screen, [0112] a projector arranged (in
viewing direction) behind the projection screen, [0113] at least
one filter array, arranged (in viewing direction) in front of the
projection screen, in which [0114] the filter array has wavelength
filter elements arranged in columns and rows, which are transparent
to light of different wavelengths (.lamda.) or different wavelength
regions (.DELTA..lamda.), [0115] the projector projects bits of
partial information of n views (A.sub.k with k=1 . . . n;
n.gtoreq.2) of a the scene or object in a defined combination of
the bits of partial information onto the projection screen
directly, so that the projection screen displays bits of partial
information of the views (A.sub.k), with the projection screen
being divided into a grid of image rendering elements
(.alpha..sub.ij) of sufficient resolution arranged in columns (i)
and rows (j), which, depending on the embodiment of the projector,
deliver light of particular wavelengths (.lamda.) or wavelength
ranges, and with each image rendering element (.alpha..sub.ij)
rendering bit(s) of partial information of at least one of the
views (A.sub.k), and in which [0116] the at least one filter array
defines propagation directions for the light delivered by the
projection screen towards the observer, with every one image
rendering element (.alpha..sub.ij) corresponding to several
wavelength filters of the filter array, and each wavelength filter
of the filter array corresponding to several image rendering
elements (.alpha..sub.ij) correlated to it, in such a way that the
straight line connecting the centroid of the cross-section area of
a visible segment of the image rendering element (.alpha..sub.ij)
and the centroid of the cross-section area of a visible segment of
the wavelength filter corresponds to one propagation direction, so
that, from every viewing position, an observer will see
predominantly bits of partial information of a first selection of
views (A.sub.k) with one eye and predominantly bits of partial
information of a second selection of views (A.sub.k) with the other
eye and thus will have a spatial impression from a great number of
viewing positions.
[0117] The combination of the bits of partial information of the
views (A.sub.k), which the projector projects onto the projection
screen, is preferably effected in the way described in DE 10003326
C2, which also gives exemplary image combination rules and
describes suitable filter arrays that can be employed, for example,
in connection with the last of the embodiments of the invention
described above. Apart from that, what has been said for the
embodiments of the invention described earlier herein with regard
to the configuration of the filter elements and the geometry of the
arrangement applies also to the embodiment described last.
[0118] To compensate imaging aberrations of the projector lens in
the embodiment described last, it may be particularly advantageous
if the form of the filter elements is varied at least in part.
[0119] All arrangements described so far may also be assembled in a
modular embodiment so as to achieve particularly long image
diagonals. Moreover it is feasible, for special purposes, to
provide a lens, preferably a Fresnel lens, in front of the
arrangements according to the invention, so that the observer(s)
can see a real or virtual image of the autostereoscopic projection
device.
[0120] With all embodiments described, the object of the invention
can be accomplished superbly: The autostereoscopic projection
devices as disclosed by the invention provide improved perception
even of images of larger dimensions, and they are made from simple
or easily manufactured units or subassemblies. Depending on the
geometry of the arrangement, a spatial impression is provided
several observers.
[0121] The advancement of the invention described below provides
improved perception of images of yet larger dimensions.
[0122] In that respect, the invention provides for a method for
autostereoscopic projection in which at least one projector
projects bits of partial image information of at least two views
A.sub.k (k=1 . . . n, n.gtoreq.2) of a scene or object onto the
rear side of a holographic screen, in which [0123] the holographic
screen has a multitude of holographic optical elements (HOE)
arranged in a grid of columns and/or rows, and [0124] each HOE
displays the light incident from the at least one projector by
means of at least one of the following types, or combination of
types, of optical imaging: [0125] a) Imaging by means of a lens,
preferably a cylindrical lens arranged vertically or obliquely to
the vertical, [0126] b) Diffusely transparent or translucent
imaging, with subsequent imaging by means of a lens, preferably a
cylindrical lens arranged vertically or obliquely to the vertical,
[0127] c) Imaging by means of a prism, [0128] d) Diffusely
transparent or translucent imaging, with subsequent imaging by
means of a prism, [0129] e) Imaging through a polygonal polarizing
filter and/or stepped neutral density filter and/or wavelength
filter, with a wavelength filter transmitting light of a specified
wavelength or of one or several specified wavelength ranges, [0130]
f) Imaging according to e) plus diffusely transparent or
translucent imaging, [0131] g) Imaging according to f) and
subsequently according to e), [0132] h) Imaging by means of an
optical flat, [0133] i) Imaging by diffraction, so that the imaging
actions of the multitude of HOEs define a multitude of propagation
directions for the light cast toward the observer by the front side
of the holographic screen, with each HOE defining one or several
light propagation directions for the light incident on it, which
corresponds to bits of partial image information of at least one of
at least two views projected, so that, from every viewing position,
an observer will see predominantly bits of partial information of a
first selection of views (A.sub.k) with one eye and predominantly
bits of partial information of a second selection with the other
eye and thus will have a spatial impression from a great number of
viewing positions.
[0134] "Predominantly" in this context means, e.g., that about 90%
of the bits of partial information seen by the left eye of an
observer originates from a first, and about 10% from a second view
of a scene or object, so that in this case the first view is
predominant. Simultaneously, about 80% of the bits of partial
information seen by the observer's right eye may originate from the
second view while about 20% may be a mix of a third and a fourth
view, without any detriment to the spatial impression.
[0135] In the context of the invention, "holographic optical
elements (HOEs)" means individual surface segments of the
holographic screen.
[0136] The method according to the invention is characterized by
the fundamental relationship that the light propagation direction
defined by each HOE for every light ray incident on it is a
one-to-one function of the ray's direction of incidence. The term
"light propagation directions" also includes the (possibly many)
light exit directions that represent the highest intensity of the
light projected within a certain solid angle.
[0137] Under certain circumstances, types of imaging other than
those given under a) through h) above may also be feasible for
display by the HOEs.
[0138] It may be advantageous that all HOEs implement the same
type, or combination of types, of imaging out of a) through h). For
certain applications, however, it may be preferable that at least
two of the HOEs implement a pair of different types, or combination
of types, of imaging out of a) through h).
[0139] Furthermore, the method according to the invention may
provide that at least one HOE implements at least two of the types,
or combination of types, of imaging out of a) through h); in
particular, for example, one HOE may simultaneously implement many
(different) images according to e) by implementing a whole array of
several filter elements.
[0140] Furthermore, an HOE can be designed in such a way that it
implements different imaging types for light incident from two
different directions. By means of such a design it would be
possible, e.g., that a scattering surface belonging to the imaging
features of an HOE receives light quantities from different
projectors, which are imaged by one and the same HOE in different
ways, especially in different directions.
[0141] Diffusely imaging features of the HOEs, if provided, may
widely differ in embodiment. Preferably, diffuse scattering within
the optical imaging is implemented in such a way that the light is
scattered essentially along the vertical, or along a direction that
is inclined relative to the vertical. Diffuse scattering by the
HOEs may also be accomplished through diffraction.
[0142] The order of magnitude of the HOEs or the optical components
represented by them such as prisms, lenses or filters approximately
corresponds to the order of magnitude of the pixels of the images
seen on the holographic screen. The respective height of an HOE
corresponds to the size of a pixel or subpixel, whereas the width
of an HOE may vary between approximately the width of one pixel of
a view and approximately the width of one cycle of pixels of
several views. Deviations from these sizes are possible, of course;
in particular, light of a pixel projected by the projector or one
of the projectors may simultaneously be incident on several
HOEs.
[0143] In another embodiment, at least two of the HOEs on the
holographic screen deviate from one another in their outer
dimensions and/or their outer shape. This design contributes to the
circumstance that an observer's eye will, from many viewing
positions, predominantly but not exactly see bits of partial image
information of a selection of views. This also helped if the
relative positions of the area centroids of at least two of the
HOEs on the holographic screen deviate from each other by an offset
equal to a non-integral multiple of the width and/or height of one
of the said HOEs. If then, for example, all HOEs had the same
dimensions, this property would correspond to the relative partial
offset between them, e.g., by one third or one quarter of the (in
this case, common) HOE width and/or height.
[0144] In another advantageous embodiment, at least one of the HOEs
displays light of different wavelength ranges in pairs of disjoint
directions. Thus it is possible, especially in case of projection
devices with full-color pixels (e.g. DMD or color slide), to
apparently increase the perceived resolution of the 3D image, e.g.,
by a factor of 3 for the horizontal screen direction.
[0145] Further, the grid in which the HOEs are arranged on the
holographic screen is preferably an orthogonal grid. It is also
possible, though, that the said grid in which the HOEs are arranged
on the holographic screen is a non-orthogonal one, preferably one
in which the row direction intersects the column direction at an
angle unequal to 90 degrees. In this connection, columns or rows
may also be of a wavy shape. The latter properties can be used to
advantage especially if imaging aberrations of the projection
lenses are to be compensated by means of a correspondingly
pre-distorted arrangement of the HOEs on the holographic
screen.
[0146] Furthermore, the method according to the invention may also
be characterized in that at least one HOE defines, for the light
from at least one direction of incidence, at least two light
propagation directions simultaneously. This can have the favorable
effect that there results, along a certain line in the viewing
space (e.g., a line parallel to the holographic screen), a
repetitive cycle of views, e.g., a cycle repeated several times in
which the observer will, in succession along the said line,
predominantly see bits of partial image information of view 1,
followed by views 2, 3 etc., up to view 8, upon which the cycle
starts again with bits of partial image information of view 1.
[0147] Furthermore, the action of the HOEs also defines how often
the cycles of views (e.g., from view 1 through view 8) are
essentially perceived by a defined observer eye moving along a line
as described above. Depending on the application, the cycle may be
repeated once, twice or more often along a line that is, e.g.,
parallel to the holographic screen.
[0148] Besides, the method can be implemented in such a way that at
least two projectors are provided, with each projector projecting
either bits of partial image information of only one view of a
scene or object, or simultaneously bits of partial image
information of at least two views of a scene or object. Of course,
this applies also to more than two projectors. The decisive point
is that bits of partial image information of at least two views are
projected.
[0149] To avoid pseudoscopic effects, the method according to the
invention may further provide, for an observer's eye in the viewing
space, at least one viewing position in which the holographic
screen essentially displays none of the light projected by the
projectors. This is easily possible in that the types of imaging,
or their combinations, implemented by the HOEs are so designed that
a certain zone of the viewing space is essentially kept free of
light. Avoiding pseudoscopy is possible here especially if such a
dark zone is located between the end and the start of a cycle of
(e.g., eight) views.
[0150] Further, the holographic screen can be so designed with
regard to its action that the respective projectors are spaced at a
distance from each other that is greater than their spatial
dimensions. This makes the effort involved in a both vertical and
lateral arrangement of the projectors for adjusting the projection
lenses at an observer's interpupillary distance obsolete. The
desired effect is accomplished by appropriately defined imaging
types or light propagation directions.
[0151] In addition, the projection may also be performed in a time
sequence. For this purpose, at least one, but preferably each
projector projects bits of partial image information of at least
one view of the scene or object at particular times only,
preferably at a specified frequency between 10 Hz and 60 Hz. This
can be done in several versions: Firstly, a projector may, at a
first point of time, project only one view. This is followed by a
second view projected onto the holographic screen by a second
projector from a different direction, etc. The last projector is,
in turn, followed by the first one, etc.
[0152] Further, the combination structure for combining the bits of
partial image information of different views on at least one of the
projectors may vary in time. Of course, the respective projector
simultaneously projects bits of image formation of at least two
views. In addition, the number of views from which the respective
bit of partial information projected by a projector originates may
also vary in time. Further sequential embodiments of the method
according to the invention can be derived.
[0153] The sequential illumination is especially used for an
improvement in separation of the light projected, i.e. of the
projected bits of partial image information of several views with
regard to different light exit directions. With the projections by
different projectors from different directions being sequenced in
time, it is possible, e.g., to partially compensate imperfections
of the HOEs.
[0154] In another special embodiment, at least two projectors are
provided, and the light from at least one projector is displayed in
such a way that it can be perceived from the front side within a
solid angle of at least 0.3.pi.*sr, so that the light from the said
projector is seen by the observer as an essentially two-dimensional
image, because both eyes of the observer are located within the
said solid angle and thus are offered essentially non-disparate
image information. Here again it is feasible, e.g., that the
projector, the light of which is seen as a two-dimensional image,
is switched on only temporarily, i.e. exactly at the point in time
at which a 2d display is desired. In some cases, the solid angle
may be smaller than 0.3.pi.*sr while the display may still be
two-dimensional.
[0155] Each projector used comprises, e.g., either at least one DMD
chip, one LCD component, one CRT or one laser. Of course, other
projector types are feasible as well.
[0156] The object of the invention is also accomplished with an
autostereoscopic projection arrangement, comprising [0157] at least
one projector for the backprojection of bits of partial image
information from at least two views Ak (k=1 . . . n, n.gtoreq.2) of
a scene or object onto a holographic screen, in which [0158] the
holographic screen has a multitude of holographic optical elements
(HOEs) arranged in a grid of columns and/or rows, and in which
[0159] each HOE displays the light incident from at least one
projector by means of at least one of the following optical imaging
types or combinations of imaging types: [0160] a) Imaging by means
of a lens, preferably a cylindrical lens arranged vertically or
obliquely to the vertical, [0161] b) Diffusely transparent or
translucent imaging, with subsequent imaging by means of a lens,
preferably a cylindrical lens arranged vertically or obliquely to
the vertical, [0162] c) Imaging by means of a prism, [0163] d)
Diffusely transparent or translucent imaging, with subsequent
imaging by means of a prism, [0164] e) Imaging through a polygonal
polarizing filter and/or stepped neutral density filter and/or
wavelength filter, with a wavelength filter transmitting light of a
specified wavelength or one or several specified wavelength ranges,
[0165] f) Imaging according to e) plus diffusely transparent or
translucent imaging, [0166] g) Imaging according to f) and
subsequently according to e), [0167] h) Imaging by means of an
optical flat, [0168] i) Imaging by diffraction, so that the imaging
actions of the multitude of HOEs define a multitude of propagation
directions for the light cast toward the observer by the front side
of the holographic screen, with each HOE defining one or several
light propagation directions for the light incident on it, which
corresponds to bits of partial image information of at least one of
at least two views projected, so that, from every viewing position,
an observer will see predominantly bits of partial information of a
first selection of views (A.sub.k) with one eye and predominantly
bits of partial information of a second selection with the other
eye, and thus will have a spatial impression from a great number of
viewing positions.
[0169] "Predominantly" in this context means, e.g., that about 90%
of the bits of partial information seen by the left eye of an
observer originates from a first, and about 10% from a second view
of a scene or object, so that in this case the first view is
predominant. Simultaneously, e.g., about 80% of the bits of partial
information seen by the observer's right eye may originate from the
second view while about 20% may be a mix of a third and a fourth
view, without any detriment to the spatial impression. The method
according to the invention is characterized by the fundamental
relationship that the light propagation direction defined by each
HOE for every light ray incident on it is a one-to-one function of
the ray's direction of incidence. Under certain circumstances,
types of imaging other than those given under a) through i) above
may also be feasible for display by the HOEs.
[0170] Further advantageous embodiments of this version of the
invention are described in the dependent claims.
[0171] The object of the invention is also accomplished by a method
of autostereoscopic projection in which at least one projector
projects bits of partial image information from at least two views
A.sub.k (k=1 . . . n, n.gtoreq.2) of a scene or object onto the
front side of a holographic screen, in which [0172] the holographic
screen has a multitude of holographic optical elements (HOEs)
arranged in a grid of columns and/or rows, and in which [0173] each
HOE displays the light incident from at least one projector by
means of at least one of the following optical imaging types or
combinations of imaging types: [0174] a) Imaging by means of a
concave or convex mirror, preferably a cylindrical mirror arranged
vertically or obliquely to the vertical, [0175] b) Diffuse
reflection, with subsequent imaging by means of a concave or convex
mirror, preferably a cylindrical mirror arranged vertically or
obliquely to the vertical, [0176] c) Imaging by means of a doublet
or triplet of mirrors, [0177] d) Diffuse reflection, with
subsequent imaging by means of a doublet or triplet of mirrors,
[0178] e) Imaging through a polygonal polarizing filter and/or
stepped neutral density filter and/or wavelength filter, with a
wavelength filter transmitting light of a specified wavelength or
one or several specified wavelength ranges, [0179] f) Imaging
according to e), plus diffuse reflection and subsequent imaging
according to e) again, [0180] g) Diffuse reflection, and subsequent
imaging by means of an optical flat, [0181] h) Diffuse reflection,
and subsequent imaging by means of a prism, [0182] i) Imaging by
diffraction, so that the imaging actions of the multitude of HOEs
define a multitude of propagation directions for the light cast
toward the observer by the front side of the holographic screen,
with each HOE defining one or several light propagation directions
for the light incident on it, which corresponds to bits of partial
image information of at least one of at least two views projected,
so that, from every viewing position, an observer will see
predominantly bits of partial information of a first selection of
views (A.sub.k) with one eye and predominantly bits of partial
information of a second selection with the other eye, and thus will
have a spatial impression from a great number of viewing
positions.
[0183] "Predominantly" in this context means, e.g., that about 90%
of the bits of partial information seen by the left eye of an
observer originates from a first, and about 10% from a second view
of a scene or object, so that in this case the first view is
predominant. Simultaneously, e.g., about 80% of the bits of partial
information seen by the observer's right eye may originate from the
second view while about 20% may be a mix of a third and a fourth
view, without any detriment to the spatial impression. The method
according to the invention is characterized by the fundamental
relationship that the light propagation direction defined by each
HOE for every light ray incident on it is a one-to-one function of
the ray's direction of incidence. Under certain circumstances,
types of imaging other than those given under a) through i) above
may also be feasible for display by the HOEs.
[0184] Further advantageous embodiments of this version of the
invention are described in the dependent claims.
[0185] The object of the invention is also accomplished with
autostereoscopic projection arrangement comprising [0186] at least
one projector for the projection von bits of partial image
information from at least two views A.sub.k (k=1 . . . n,
n.gtoreq.2) of a scene or object onto the front side of a
holographic screen, in which [0187] the holographic screen has a
multitude of holographic optical elements (HOEs) arranged in a grid
of columns and/or rows, and in which [0188] each HOE displays the
light incident from at least one projector by means of at least one
of the following optical imaging types or combinations of imaging
types: [0189] a) Imaging by means of a concave or convex mirror,
preferably a cylindrical mirror arranged vertically or obliquely to
the vertical, [0190] b) Diffuse reflection, with subsequent imaging
by means of a concave or convex mirror, preferably a cylindrical
mirror arranged vertically or obliquely to the vertical, [0191] c)
Imaging by means of a doublet or triplet of mirrors (corner
reflector), [0192] d) Diffuse reflection, with subsequent imaging
by means of a doublet or triplet of mirrors, [0193] e) Imaging
through a polygonal polarizing filter and/or stepped neutral
density filter and/or wavelength filter, with a wavelength filter
transmitting light of a specified wavelength or one or several
specified wavelength ranges, [0194] f) Imaging according to e),
plus diffuse reflection and subsequent imaging according to e)
again, [0195] g) Diffuse reflection, and subsequent imaging by
means of an optical flat, [0196] h) Diffuse reflection, and
subsequent imaging by means of a prism, [0197] i) Imaging by
diffraction, so that the imaging actions of the multitude of HOEs
define a multitude of propagation directions for the light cast
toward the observer by the front side of the holographic screen,
with each HOE defining one or several light propagation directions
for the light incident on it, which corresponds to bits of partial
image information of at least one of at least two views projected,
so that, from every viewing position, an observer will see
predominantly bits of partial information of a first selection of
views (A.sub.k) with one eye and predominantly bits of partial
information of a second selection with the other eye, and thus will
have a spatial impression from a great number of viewing
positions.
[0198] Further advantageous embodiments are described in the
dependent claims.
[0199] In principle, it applies to each embodiment of the
arrangement according to the invention that an increase in the
number of projectors permits an increase in resolution and/or the
number of views perceived on the holographic screen. Besides it is
feasible that a projected pixel represents a mix of bits of image
information from at least two different views.
[0200] The invention also relates to methods for the manufacture of
a holographic screen for use in one of the methods or arrangements
described above. The method of manufacture comprises the following
operations: [0201] a) Manufacture of an optical arrangement
containing a multitude of optical components providing the optical
imaging types or type combinations, or combinations thereof,
specified in the independent claim 1 or 31; [0202] b) Positioning
of an (undeveloped) holographic screen in the vicinity of the said
optical arrangement; [0203] c) Exposure of the holographic screen
to one or several coherent light sources, in which the holographic
screen is preferably struck by a reference beam coming directly
from the light source and an object beam which, coming also from
the light source, has passed the said optical arrangement;
preferably, this operation c) is repeated several times, preferably
in such a way that every time that operation c) is executed the
light source is given a different position relative to the said
optical arrangement and, optionally, a different optical
arrangement is used; [0204] d) Development of the holographic
screen.
[0205] It will not be possible in every case to actually
manufacture the optical arrangement needed. In such a case the
method described below can be used alternatively to that described
above. The alternative method comprises the following operations:
[0206] a) Selection of a multitude of optical components providing
the optical imaging types or type combinations, or combinations
thereof, specified in the independent claims 1 or 31, and
arrangement of these components in a grid of rows and/or columns;
[0207] b) Computation of the respective holographic interference
patterns for the imaging types or combinations; [0208] c) Exposure
of the holographic screen to one or several coherent light sources
so that the computed holographic interference pattern(s) are
written onto the holographic screen; [0209] d) Development of the
holographic screen.
[0210] In special cases it is further possible to manufacture the
holographic screen in the following way: [0211] Manufacture of at
least two holographic screens according to either of the two
methods described above; [0212] Assembling the at least two
holographic screens thus manufactured into one holographic
screen.
[0213] It is thus possible to make the holographic screen as a
stack of several layers. The layers may be joined to each other,
e.g., by lamination.
[0214] With an additional advancement of the invention, described
below, it is accomplished that the observer or observers can move
about within the largest possible viewing range without any
deterioration in the quality of the 3D display perceived, so that
the arrangement can be used, in particular, for 3D projections of
large images sized up to several square meters.
[0215] According to the invention, such an arrangement for the
projection of a three-dimensionally perceived image comprises
[0216] at least one projection unit suitable for the projection of
at least one image containing bits of image information from a
number of n views (n.gtoreq.2) of a scene or object; [0217] a
projection screen comprising a multitude of reflectors in an
array-type arrangement, in which the reflectors reflect the light
originating from the projection unit largely irrespective of the
respective direction of light incidence in such a way that each
illuminated reflector emits a cone of reflected light in which at
least one line lying in a plane parallel to the plane of the
projection screen and tangent to the spatial course of the
intensity maximum in the said cone of reflected light has an angle
of inclination of 0.degree.<.alpha.<90.degree. relative to
the vertical extension of the edge of the said projection screen if
this vertical extension is projected parallelly onto the said
parallel plane.
[0218] Preferably, several such cones of reflected light are
superimposed in such a way that the spatial courses of the
respective intensity maximums are essentially equal. In this way it
is accomplished that, from or several (monocular) viewing
positions, different reflections (which function as partial image
elements or partial image areas) are perceived with approximately
equal brightness.
[0219] The object of the invention is also accomplished by the
embodiment of an arrangement for the projection of a
three-dimensionally perceived image, comprising [0220] at least one
projection unit suitable for the projection of at least one image
containing bits of image information from a number of n views
(n.gtoreq.2) of a scene or object; [0221] a projection screen
comprising a multitude of reflectors in an array-type arrangement
of essentially identical size and shape, in which the said
reflectors reflect the light originating from the projection unit
within a solid angle smaller than 1 .pi.*sr, characterized in that
at least two of the reflectors are horizontally and/or vertically
offset relative to each other by a distance that is not an integral
multiple of the width of one of these reflectors in case of a
horizontal offset, or the height of a reflector in case of a
vertical offset.
[0222] The object of the invention is also accomplished by the
embodiment of an arrangement for the projection of a
three-dimensionally perceived image, comprising [0223] at least one
projection unit suitable for the projection of at least one image
containing bits of image information from a number of n views
(n.gtoreq.2) of a scene or object; [0224] a projection screen
comprising a multitude of shaped reflectors in an array-type
arrangement, characterized in that at least two of the reflectors
differ from each other in at least one of the parameters, viz.
shape, size or direction-dependent reflectance.
[0225] In all embodiments of the arrangements according to the
invention, the projection unit may contain a DMD chip or one or
several LCD light modulators. The projection unit may further
contain a laser projector.
[0226] In addition, one or several filter arrays may be provided in
front of the projection screen (in viewing direction), with each
filter array containing a multitude of filter elements which are
arranged in columns and rows and which are either transmissive
(with a defined transmittance) or opaque to light of particular
wavelengths/wavelength ranges. This provides an added directional
selectivity of the projected or reflected bits of partial image
information.
[0227] For example, in all three embodiments, each individual
reflector or simultaneously several reflectors on the projection
screen may be formed by two plane mirrors arranged at a certain
angle, preferably 90.degree., to each other, and a lenticular. In
this case the intersection edge of the respective two plane mirrors
would, e.g., be inclined at an angle of 7.degree. relative to the
vertical.
[0228] Instead of this it is also feasible that each individual
reflector or simultaneously several reflectors on the projection
screen may consist of a metal coat on a plastic substrate.
Furthermore, the base surface of the projection screen may be
either plane or curved.
[0229] In a special embodiment of each of the three basic
embodiments described so far, one or several reflectors of the
projection screen may be supported in a rotatable fashion, in which
preferably the combination structure of the projected bits of image
information of the n views (n.gtoreq.2) of a scene or object are
varied in time for at least one projection unit, so that the light
originating from the projection unit or one of the projection units
and projected onto one of the rotatable reflectors, preferably
originates from bits of image information of different views
alternating in time, so that the said reflector reflects bits of
image information of different views in different directions at
different times.
[0230] Moreover, one or several reflectors of the projection screen
may have reflection properties that depend on wavelength.
Preferably, in this embodiment, some reflectors specially reflect
light of different wavelengths in different directions.
[0231] In further exemplary embodiments, means for folding the beam
between the projection unit and the projection screen are provided
in addition to decrease the spatial extension of the arrangement
according to the invention. Beam folding in image projection is
known to one skilled in the art and needs no further explanation
here.
[0232] In an advantageous embodiment, at least four projection
units are used, which project their images or bits of partial image
information onto the projection screen from different directions.
This permits the projection of a greater number of different views
of a scene or object than it would be possible with, e.g., just one
or two projection units, und thus is of great advantage in that it
provides greater freedom of movement for observers.
[0233] The projection unit, or each of the projection units, is
spaced from the projection screen by a distance of, e.g., between
0.5 and 20 meters.
[0234] The object of the invention is also accomplished by an
embodiment of an arrangement for the projection of a
three-dimensionally perceived image, comprising [0235] at least two
projection units, each of which is suitable for the projection of
at least one image, which contains bits of image information from a
number of n views (n.gtoreq.2) of a scene or object; [0236] a
projection screen comprising a multitude of reflectors in an
array-type arrangement, characterized in that at least one
reflector simultaneously receives light from at least two
projection units, in which the light originating from different
projection units is maximally reflected in essentially different
spatial directions.
[0237] Even in this fourth embodiment of the invention, each
projection unit preferably contains either a DMD chip or one or
several LCD light modulators, or a laser projector. In the case of
laser projectors, the low divergence of the light beams is of great
advantage, as highly defined images can be produced without
problems. Preferably, each projection unit can perform this
completely without any convergent imaging optics.
[0238] For special embodiments, this arrangement is additionally
provided with one or several filter arrays arranged in front of the
projection screen (in viewing direction), with each filter array
containing a multitude of filter elements which are arranged in
columns and rows and which are either transmissive (with a defined
transmittance) or opaque to light of particular
wavelengths/wavelength ranges.
[0239] Each individual reflector or simultaneously several
reflectors on the projection screen may, e.g., be formed by two
plane mirrors arranged at a certain angle, preferably 90.degree.,
to each other, and a lenticular.
[0240] Instead of this it is also feasible that each individual
reflector or simultaneously several reflectors on the projection
screen may consist of a metal coat on a plastic substrate.
Furthermore, the base surface of the projection screen may be
either plane or curved.
[0241] In a special embodiment of the fourth embodiment described
so far, one or several reflectors of the projection screen may be
supported in a rotatable fashion, in which preferably the
combination structure of the projected bits of image information of
the n views (n.gtoreq.2) of a scene or object are varied in time
for at least one projection unit, so that the light originating
from the projection unit or one of the projection units and
projected onto one of the rotatable reflectors, preferably
originates from bits of image information of different views
alternating in time, so that the said reflector reflects bits of
image information of different views in different directions at
different times.
[0242] Moreover, one or several reflectors of the projection screen
may have reflection properties that depend on wavelength.
Preferably, in this embodiment, some reflectors specially reflect
light of different wavelengths in different directions.
[0243] In further exemplary embodiments, means for folding the beam
between the projection unit and the projection screen are provided
in addition to decrease the spatial extension of the arrangement
according to the invention. Beam folding in image projection is
known to one skilled in the art and needs no further explanation
here.
[0244] In an advantageous embodiment, at least four projection
units are used, which project their images or bits of partial image
information onto the projection screen from different directions.
This permits the projection of a greater number of different views
of a scene or object than it would be possible with, e.g., just one
or two projection units, und thus is of great advantage in that it
provides greater freedom of movement for observers.
[0245] The projection unit, or each of the projection units, is
spaced from the projection screen by a distance of, e.g., between
0.5 and 20 meters.
[0246] In a particularly preferable embodiment of the
autostereoscopic projection arrangement according to the invention,
a filter array in the form of a color mask is provided in the beam
path between the projector/the projectors and the projection
screen, this color directs different colors, preferably red, green
and blue, onto subpixels belonging to a pixel of the projection
screen, so that the subpixels display not only the pure colors red,
green and blue, but also mixed colors and, thus, a greater number
of hues per subpixel can be displayed and the resolving capability
of the projection screen is increased.
[0247] The width I.sub.new of the colors that can be displayed per
pixel results, e.g., from l new = l .times. n 2 .times. n - 1
##EQU3## in which I is the size of one subpixel and n the number of
subpixels per pixel; alternatively, the number p.sub.new of the
views displayable per pixel is increased according to the function
p new = p .times. 2 .times. n - 1 n ##EQU4## in which n is the
number of subpixels per pixel and p the number of different views
of the scene or object that can be displayed, preferably with n=3
and p=8.
[0248] The width I.sub.new may vary from color to color. In this
way it is feasible to influence and specify not only the width, but
also the shapes or outline geometries of the image rendering
elements. A filter element may be composed of several smaller
partial filter elements.
[0249] The said color mask may be configured as a lens, an HOE or
another optical element capable of effecting a spectral separation
of the incident light.
[0250] In each of the embodiments described it is feasible that an
image rendering element of the smallest physical size, of any of
the projection units, is controlled either by the information of an
individual image rendering element of a view of a scene or object,
or by mixed image information resulting, e.g., as the weighted mean
of the bits of image information of image rendering elements of at
least two views of a scene or object. Exemplary image combination
structures are given, e.g., in the patent specification DE 100 03
326 C2 mentioned before, and in DE 101 45 133 C1.
[0251] In each of the four general embodiments, the principle of
displaying a spatially perceivable image is essentially identical:
Bits of partial image information of different views of a scene or
object are reflected essentially into different viewing directions,
so that each observer will see predominantly a first selection of
views with one eye, and predominantly a second selection of views
with the other eye, so that a stereo contrast is accomplished that
is sufficient for a spatial impression.
[0252] The number of projectors can be reduced if a projector
sequentially projects bits of information of different views while
the direction of the optical axis is varied at an appropriate
frequency, e.g., by reflectors that deflect the beams as a function
of time.
[0253] Moreover, the filter array positioned closest to the
observer may be partially reflecting in order to generate a 2D
display on this filter array, which in this case is used as a
projection screen.
[0254] Below, the invention will be explained in more detail with
reference to the accompanying drawing in which:
[0255] FIG. 1 is a sketch illustrating the principle of the
arrangements according to the invention,
[0256] FIG. 2 illustrates the projector-side filter array of a
first embodiment of the invention (detail), suitable for, e.g.,
eight projectors,
[0257] FIG. 3 illustrates the observer-side filter array of a first
embodiment of the invention (detail),
[0258] FIG. 4 illustrates the image structure formed on the
projection screen in the first embodiment of the invention, this
image structure being composed of bits of partial information of
different views (detail),
[0259] FIG. 5 and FIG. 6 illustrate a possible mix of views each
visible to an observer's eye in a viewing position in the first
embodiment of the invention (detail),
[0260] FIG. 7 illustrates the projector-side filter array of a
second embodiment of the invention (detail), also suitable for
eight projectors,
[0261] FIG. 8 illustrates the observer-side filter array of the
second embodiment of the invention (detail),
[0262] FIG. 9 illustrates the image structure formed on the
projection screen in the second embodiment of the invention, this
image structure being composed of bits of partial information of
different views (detail),
[0263] FIG. 10 and FIG. 11 illustrate a possible mix of views each
visible to an observer's eye in a viewing position in the second
embodiment of the invention (detail),
[0264] FIG. 12 illustrates the first projector-side filter array of
a third embodiment of the invention (detail), also suitable for
eight projectors,
[0265] FIG. 13 illustrates the second projector-side filter array
of a third embodiment of the invention (detail),
[0266] FIG. 14 illustrates the observer-side filter array of the
third embodiment of the invention (detail),
[0267] FIG. 15 illustrates the image structure formed on the
projection screen in the third embodiment of the invention, this
image structure being composed of bits of partial information of
different views (detail),
[0268] FIG. 16 illustrates the projector-side filter array of a
fourth embodiment of the invention (detail), also suitable for
eight projectors,
[0269] FIG. 17 illustrates the observer-side filter array of the
fourth embodiment of the invention (detail),
[0270] FIG. 18 illustrates the image structure formed on the
projection screen in the fourth embodiment of the invention, this
image structure being composed of bits of partial information of
different views (detail),
[0271] FIG. 19 and FIG. 20 illustrate a possible mix of views each
visible to an observer's eye in a viewing position in the fourth
embodiment of the invention (detail),
[0272] FIG. 21 illustrates the projector-side filter array of a
fifth embodiment of the invention (detail), suitable for a single
DMD projector,
[0273] FIG. 22 illustrates the observer-side filter array of the
fifth embodiment of the invention (detail),
[0274] FIG. 23 illustrates the image structure formed on the
projection screen in the fifth embodiment of the invention, this
image structure being composed of bits of partial information of
different views (detail), the bits of partial information of the
different views being rendered in colors (wavelength ranges)
differing from view to view,
[0275] FIG. 24 illustrates diverse possible outlines of filter
elements in the arrangements according to the invention,
[0276] FIG. 25 is a sketch illustrating the principle of
constructing an arrangement according to the invention with
back-projection,
[0277] FIG. 26 illustrates an exemplary first filter structure
implemented by at least one HOE or simultaneously several HOEs
(detail),
[0278] FIG. 27 illustrates an exemplary second filter structure
implemented by at least one HOE or simultaneously several HOEs
(detail),
[0279] FIG. 28 illustrates an exemplary image combination structure
for the composition of an image from bits of partial image
information of several views,
[0280] FIG. 29 and FIG. 30 illustrate exemplary views mixes visible
to one eye each,
[0281] FIG. 31 illustrates another example for the effect of a HOE
(shown schematically),
[0282] FIG. 32 is an exemplary model illustrating the effect of
HOEs on the holographic screen of arrangements according to the
invention,
[0283] FIG. 33 illustrates an exemplary image combination structure
using four views,
[0284] FIG. 34 illustrates another exemplary model illustrating the
effect of the HOEs on the holographic screen of arrangements
according to the invention,
[0285] FIG. 35 illustrates an embodiment with a holographic 3D
back-projection screen,
[0286] FIG. 36 illustrates an example with vertically aligned eye
positions,
[0287] FIG. 37 illustrates an example with obliquely aligned eye
positions,
[0288] FIG. 38 illustrates an embodiment with projectors, each of
which showing bits of image information of at least two views.
[0289] FIG. 1 is a sketch illustrating the principle of the
arrangements according to the invention. The sketch is not to
scale. As described above, the arrangement shown, according to the
invention, comprises the following components: [0290] at least two
projectors 4; (for the sake of clarity, the drawing shows only four
projectors, although there might be, e.g., eight or more), [0291] a
projection screen 3, [0292] at least two filter arrays F.sub.1,
F.sub.2, with filter array F.sub.1 arranged between the projection
screen 3 and the projectors 4, i.e. behind the projection screen 3
(in the viewing direction of the observer 5), and filter array
F.sub.2 arranged in front of the projection screen 3 (in the
viewing direction of the observer 5).
[0293] As will be explained in detail below for the various
embodiment versions, all filter arrays F.sub.1, F.sub.2 have
wavelength filter elements arranged in columns and rows, which are
transparent to light of different wavelengths .lamda. or different
wavelength regions .DELTA..lamda.. The projectors 4 project bits of
partial information from n views A.sub.k (with k=1 . . . n;
n.gtoreq.2) of a scene or object through at least one filter array
F.sub.1 and onto the projection screen 3, so that the projection
screen 3 makes optically visible bits of partial information of
views A.sub.k in a combination or mix defined by the geometry of
the arrangement, the projection screen 3 being divided into a grid
of sufficient resolution consisting of image rendering elements
.alpha..sub.ij in columns i and rows j, which, depending on the
embodiment of the filter array F.sub.1 and the projectors 4,
deliver light of particular wavelengths .lamda. or wavelength
ranges, each image rendering element .alpha..sub.ij rendering a
bit, or bits, of partial information of at least one of the views
A.sub.k.
[0294] Propagation directions are defined for the light radiated
toward the observer 5 by the projection screen 3 through the at
least one filter array F.sub.2, arranged (in viewing direction) in
front of the projection screen 3, so that each single image
rendering element .alpha..sub.ij corresponds with several
correlated wavelength filters of the filter array F.sub.2, or each
single wavelength filter of the filter array F.sub.2 corresponds
with several correlated image rendering elements .alpha..sub.ij in
such a way that the straight line connecting the centroid of the
cross-section area of a visible portion of the image rendering
element .alpha..sub.ij with the centroid of the cross-section area
of a visible portion of the wavelength filter corresponds to one
propagation direction, so that, from every viewing position, an
observer 5 will see predominantly bits of partial information of a
first selection of views A.sub.k with one eye and predominantly
bits of partial information of a second selection of views A.sub.k
with the other eye, resulting in a spatial impression for the
observer 5 from many viewing positions.
[0295] Advantageously, a total number of 2, 4, 8, 16, 32 or 40
projectors can be used. Excellent spatial impressions and
convenient freedom of movement for several observers at a time are
obtained with about eight or more views presented, with preferably
eight or more projectors being used for projecting the views, and
with each projector projecting exactly one view A.sub.k or bits of
partial information thereof.
[0296] As shown in FIG. 1, the arrangement described above
preferably uses exactly two filter arrays F.sub.1 and F.sub.2.
Special configurations in which more than two filter arrays are of
advantage are described below.
[0297] In a first exemplary embodiment, an arrangement as shown in
FIG. 1 is used, but with eight instead of the four projectors 4
shown on the drawing. Each of the eight projectors projects a
complete 2D view of the scene or object to be displayed;
accordingly, eight views are presented. Such 2D views may be, e.g.,
2D shots of a scene or object taken from directions having a slight
horizontal offset between them. For technical reasons, the 2D views
are provided with some raster; therefore they are projected by the
projectors as bits of partial information, e.g., with a full-color
resolution of 1 024.times.768 pixels.
[0298] The optical axes of the projectors preferably intersect at
the center of the face of the projection screen 3, with two
neighboring optical axes including an angle of approximately 3.5
degrees. The projectors are aligned accordingly, and their
projection lenses are spaced from the face center of projection
screen 3 by, e.g., 2900 mm. Advantageously, the projectors may be
arranged on a circular arc, the center of the circle being the said
face center. Preferably, all projector lenses are at the same
height behind the projection screen, viz. approximately at the
height of the face center of the projection screen. To ensure such
a location, an appropriately dimensioned mechanical stand can be
used, for example.
[0299] FIG. 2 illustrates a detail of the projector-side filter
array F.sub.1 of the first embodiment of the invention. This filter
array F.sub.1 comprises wavelength filter elements .beta..sub.1pq
in a grid of rows q.sub.1 and columns p.sub.1, which are arranged
on the filter array depending on their transmission wavelength or
their transmission wavelength range .lamda..sub.1b according to the
following function: b = p A - d Apq q A - n Am IntegerPart
.function. [ p A - d Apq q A - 1 n Am ] , ##EQU5## in which [0300]
the index A=1, since the array F.sub.1 is concerned, [0301] p.sub.1
is the index of a wavelength filter .beta..sub.1pq in a row of the
array F.sub.1, [0302] q.sub.1 is the index of a wavelength filter
.beta..sub.1pq in a column of the array F.sub.1, [0303] b is an
integer that defines, for a wavelength filter .beta..sub.1pq of the
filter array F.sub.1 in the position p.sub.1,q.sub.1, one of the
specified transmission wavelengths or wavelength ranges
.lamda..sub.1b and may adopt values between 1 and b.sub.1max,
[0304] n.sub.1m is an integer greater than zero, which preferably
corresponds to the total number n of the views A.sub.k shown by the
projectors, [0305] d.sub.1pq is a selectable mask coefficient
matrix for varying the arrangement of wavelength filters on the
array F.sub.1, and [0306] IntegerPart is a function for generating
the greatest integer that does not exceed the argument put in
square brackets.
[0307] In the above equation, p.sub.A=p.sub.1 corresponds to the
index p, and q.sub.A=q.sub.1 to the index q for the matrix
d.sub.Apq=d.sub.1pq or for the filter elements .beta..sub.1pq.
[0308] In this embodiment, several of the transmission wavelengths
or wavelength ranges .lamda..sub.1b have the same filter effects:
If .lamda..sub.1,1 and .lamda..sub.1,3 . . . .lamda..sub.1,8 are
wavelength ranges that block the entire visible spectrum,
.lamda..sub.1,2 is a filter range transparent to the visible
spectrum, and if n.sub.1m=8 and d.sub.1pq=-1=const, the resulting
filter array F.sub.1, according to the rule for generating a filter
structure, is essentially opaque and contains oblique, stepped
transparent stripes evenly distributed over the area and occupying
approximately one eighth of the total area. This is shown in FIG.
2. Here, a transparent or opaque filter element is, e.g.,
approximately 0.285 mm wide and 0.804 mm high. Other embodiments
are also feasible, of course.
[0309] FIG. 3 shows a detail of the observer-side filter array
F.sub.2 with A=2 of the first embodiment of the invention. The
parameters used are similar, but not completely identical, to those
of filter F.sub.1, viz.: .lamda..sub.2,1 and .lamda..sub.2,4 . . .
.lamda..sub.2,8 are wavelength ranges blocking the entire visible
spectrum; .lamda..sub.2,2 and .lamda..sub.2,3 are filter ranges
transparent to the visible spectrum; n.sub.2m=8, and
d.sub.2pq=-1=const. Here again, a transparent or opaque filter
element is, e.g., approximately 0.285 mm wide and 0.804 mm high,
other dimensions being feasible as well.
[0310] The filter array F.sub.1 is arranged at a distance of
z.sub.1=2 mm behind the projection screen (in viewing direction).
For the array F.sub.2 the distance is z.sub.2=(-)45 mm, but this
array is arranged in front of the projection screen (in viewing
direction), which is indicated by the minus sign. To improve the
image contrast, the filter array F.sub.2, which is located closest
to the observer, is preferably provided with an antireflection
coating. This reduces reflections of extraneous light and improves
the visibility of the spatial image.
[0311] If the projectors are aligned as described above, an image
structure results on the projection as shown as a detail in FIG. 4.
The grid with columns i and rows j has been drawn as a reference
only; of course it is not necessarily visible on the projection
screen 3. In FIG. 4, a number inside a box indicates the view
A.sub.k from which the partial information originates that is
projected to this grid position on the projection screen. The image
formed on the projection screen 3, which is composed of different
bits of partial information from the views A.sub.k, thus shows a
grid of image rendering elements .alpha..sub.ij in columns i and
rows j. The image rendering elements .alpha..sub.ij may display
light of altogether different wavelength ranges, depending on what
light arrives from the projectors at the respective spot of the
projection screen 3. If, in this exemplary embodiment, DMD/DLP
projectors are used, the image rendering elements are full-color
pixels .alpha..sub.ij.
[0312] With correct alignment, the arrangement according to the
invention is particularly efficient with regard to the utilization
of the light and of the area, since every element of the projection
screen area can receive light from at least one of the projectors.
In this way, there will not be any "permanently black spots" on the
screen, so that every element of the projection screen area
displays some bit of partial information of at least one of the
views A.sub.k.
[0313] Because of the light propagation directions defined due to
the filter F.sub.2, an observer 5 will, from every viewing
position, see predominantly bits of partial information of a first
selection of views A.sub.k with one eye, and predominantly bits of
partial information of a second selection of views A.sub.k with the
other eye, so that, from a multitude of viewing positions, the
observer 5 will have a spatial impression. FIG. 5 and FIG. 6 each
show details of a possible mix of views that can be seen by an
observer's eye in a viewing position if the first embodiment of the
invention is used. In the first position acc. to FIG. 5, the
observer's eye will, e.g., predominantly see the views 2 and 3,
whereas in the second example position acc. to FIG. 6, it will
predominantly see the views 6 and 7. If each of the observer's eyes
sees one of the mixes of views, the observer will have a spatial
impression.
[0314] Let it be noted here that in this first exemplary embodiment
the two filter arrays F.sub.1, F.sub.2 cannot be made completely
congruent by horizontally and/or vertically linear scaling. In
other words, the structures of the respective filter arrays do not
turn into each other by one- or two-dimensional magnification or
demagnification. With regard to the spatial impression, this lack
of congruence has the effect that the eye of an observer will, from
actually every viewpoint, always see a mix of bits of partial
information from several views (see also the exemplary view mixes
in FIG. 5 and FIG. 6). This completely excludes the case that an
observer's eye in any position in the viewing space sees bits of
partial information from exactly one of the views.
[0315] The projection screen 3 is translucent and preferably also
comprises a carrier substrate, e.g. a glass plate. In addition, it
may have a light-concentrating effect, i.e. a positive gain.
Excellent definition of the image rendering elements on the
projection screen is achieved if the projection screen is designed
as a very thin wafer, preferably with a thickness of less than one
millimeter. In this first embodiment, the projection screen 3 is a
flat plate with a face diagonal of approximately 50 inches and a
side ratio of 16:9.
[0316] The projectors 4 receive image data from an electronic
control system, which may comprise one or several separate units.
In this connection, the said electronic control system may consist,
e.g., of an image data source containing one PC per projector. In
other words, there are eight PCs, with each PC feeding the image
sequence of one particular view A.sub.k to one projector, as
mentioned before. The PCs are linked to each other via a trigger,
so that all eight views A.sub.k are displayed in synchronism.
Embodiments with fewer PCs are feasible just as well.
[0317] Each of the filter arrays F.sub.1 and F.sub.2 is designed as
an exposed film. Each of the filter arrays F.sub.1, F.sub.2 is
laminated onto a substrate, e.g. a glass substrate. This provides
for good mechanical stability. In the arrangement acc. to FIG. 1,
both filter arrays F.sub.1, F.sub.2 are always arranged on the
glass substrate side facing the projectors. This provides for the
best results, since the beam offsets due to the substrates are thus
minimized, compared to the reversed arrangement of the filter array
sides on the substrates.
[0318] In a second exemplary embodiment, the arrangement also
corresponds to that shown in FIG. 1, save that eight projectors 4
are used instead of the four shown on the drawing. Here again, each
of the eight projectors 4 projects a complete 2D view of the scene
or object to be displayed, so that eight views are presented. The
optical axes of the projectors 4 again intersect preferably at the
center of the face of projection screen 3, with two neighboring
optical axes including an angle of approximately 3.5 degrees. The
projectors 4 are aligned accordingly, and their lenses are spaced
at a distance of, e.g., 2900 mm from the face center of the
projection screen 3. Advantageously, the projectors 4 may be
arranged on a circular arc, the center of the circle being the said
face center. All projector lenses are at the same height behind the
projection screen 3, viz. approximately at the height of the face
center of the projection screen 3. To ensure such a location, an
appropriately dimensioned mechanical tripod can be used, for
example.
[0319] FIG. 7 illustrates a detail of the projector-side filter
array F.sub.1 with A=1 of the second embodiment of the invention.
The wavelength filter elements .beta..sub.1pq in the grid of rows
q.sub.1 and columns p.sub.1 are arranged in accordance with the
rule described repeatedly before. The parameters applied here are
as follows: .lamda..sub.1,2 . . . .lamda..sub.1,8 are wavelength
ranges blocking the entire visible spectrum, .lamda..sub.1,1 is a
filter range transparent to the visible spectrum; further,
b.sub.1max=8, n.sub.1m=8, and d 1 .times. pq = p 1 - ( ( (
IntegerPart .function. ( q 1 - 1 ) 1 2 ) + p 1 ) .times. mod
.times. .times. 8 ) q 1 ##EQU6##
[0320] Here, the function "mod" denotes the residual class with
regard of a divisor. Here, a transparent or opaque filter element
is, e.g., approximately 0.285 mm wide and approximately 0.804 mm
high. Other embodiments are also feasible, of course.
[0321] FIG. 8 shows a detail of the observer-side filter array
F.sub.2 of the second embodiment of the invention. The parameters
for generating the respective filter structure are: .lamda..sub.2,3
. . . .lamda..sub.2,16 are wavelength ranges blocking the entire
visible spectrum; .lamda..sub.2,1 and .lamda..sub.2,2 are filter
ranges transparent to the visible spectrum; b.sub.2max=16,
n.sub.2m=16, and d.sub.2pq=-1=const. Here, a transparent or opaque
filter element is, e.g., approximately 0.14236 mm wide and 0.804 mm
high, with other dimensions being possible as well.
[0322] The filter array F.sub.1 is arranged at a distance of
z.sub.1=2 mm behind the projection screen. For the array F.sub.2,
the distance is z.sub.2=(-)45 mm, but this array is arranged in
front of the projection screen (in viewing direction), which is
indicated by the minus sign. To improve the image contrast, the
filter array F.sub.2, which is located closest to the observer, is
preferably provided with an antireflection coating. This reduces
reflections of extraneous light and improves the visibility of the
spatial image.
[0323] If the projectors are aligned as described above, an image
structure results on the projection as shown as a detail in FIG. 9.
The grid with columns i and rows j has been drawn as a reference
only; of course it is not necessarily visible on the projection
screen 3. The image formed on the projection screen, composed of
different bits of partial information of the views A.sub.k, thus
shows a grid of image rendering elements .alpha..sub.ij in columns
i and rows j. The image rendering elements .alpha..sub.ij may
display light of altogether different wavelength ranges, depending
on what light is received from the projectors at the respective
spot of the projection screen. If, in this exemplary embodiment,
DMD/DLP projectors are used, the image rendering elements are
full-color pixels .alpha..sub.ij.
[0324] With correct alignment, the arrangement according to the
invention is particularly efficient with regard to the utilization
of the light and of the area, since every element of the projection
screen area can receive light from at least one of the projectors.
In this way, there will not be any "permanently black spots" on the
screen, so that every element of the projection screen area
displays some bit of partial information of at least one of the
views A.sub.k.
[0325] Because of the light propagation directions defined due to
the filter F.sub.2, an observer 5 will, from every viewing
position, see predominantly bits of partial information of a first
selection of views A.sub.k with one eye, and predominantly bits of
partial information of a second selection of views A.sub.k with the
other eye, so that, from a multitude of viewing positions, the
observer 5 will have a spatial impression. FIG. 10 and FIG. 11 each
show details of a possible mix of views that can be seen by an
observer's eye in a viewing position if the first embodiment of the
invention is used. In the first position acc. to FIG. 10, the
observer's eye will, e.g., predominantly see the views 5 and 6,
whereas in the second example position acc. to FIG. 11, it will
predominantly see the views 2 and 3. If each of the observer's eyes
sees one of the mixes of views, the observer will have a spatial
impression.
[0326] Let it be noted here that, in this second exemplary
embodiment, the two filter arrays F.sub.1, F.sub.2 cannot be made
completely congruent by horizontally and/or vertically linear
scaling. In other words, the structures of the respective filter
arrays do not turn into each other by one- or two-dimensional
magnification or demagnification.
[0327] The projection screen is translucent and preferably also
comprises a carrier substrate, e.g. a glass plate. In addition, it
may have a light-concentrating effect, i.e. a positive gain. In
this second embodiment, the projection screen is a flat plate. Here
again, the projectors used are furnished with image data by an
electronic control system, which may comprise one or several
separate units.
[0328] Each of the filter arrays F.sub.1 and F.sub.2 is designed as
an exposed film. Each of the filter arrays F.sub.1, F.sub.2 is
laminated onto a substrate, e.g., a glass substrate. This provides
for good mechanical stability. In the arrangement acc. to FIG. 1,
both filter arrays F.sub.1, F.sub.2 are always arranged on the
glass substrate sides facing the projectors 4; the glass substrates
are not shown in FIG. 1.
[0329] A third exemplary embodiment also uses an arrangement acc.
to FIG. 1; here again, eight projectors are used instead of the
four projectors on the drawing. In addition, a third filter F.sub.3
is provided between filter F.sub.1 and the projection screen 3.
Filter F.sub.3 is not shown in FIG. 1. Each of the eight projectors
again projects a complete 2D view of the scene or object, so that
eight views are displayed.
[0330] The optical axes of the projectors intersect preferably at
the face center of the projection screen 3, with two neighboring
optical axes including an angle of approximately 3.5 degrees. The
projectors 4 are aligned accordingly, and their projection lenses
have a distance of, e.g., 2900 mm from the face center of the
projection screen 3. Advantageously, the projectors may be arranged
on a circular arc, the center of the circle being the said face
center. Preferably, all projector lenses are at the same height
behind the projection screen, viz. approximately at the height of
the face center of the projection screen. To ensure such a
location, an appropriately dimensioned mechanical tripod can be
used, for example.
[0331] FIG. 12 shows a detail of the first projector-side filter
array F.sub.1 of the third embodiment of the invention. The
wavelength filter elements .beta..sub.1pq in the grid of rows
q.sub.1 and columns p.sub.1 are arranged according to the rule
described repeatedly before; the parameters selected here are as
follows: In this embodiment again, several of the transmission
wavelengths or wavelength ranges .lamda..sub.1,b have the same
filter effects: .lamda..sub.1,1 and .lamda..sub.1,3 . . .
.lamda..sub.1,8 are wavelength ranges blocking the entire visible
spectrum, .lamda..sub.1,2 is a filter range transparent to the
visible spectrum; n.sub.1m=8, and d.sub.1pq=-1=const. Here, a
transparent or opaque filter element is, e.g., approximately 0.2847
mm wide and approximately 0.8044 mm high. Other embodiments are
also feasible, of course.
[0332] FIG. 13 shows a detail of the second projector-side filter
array F.sub.3, with A=3, of the third embodiment of the invention.
The wavelength filter elements .beta..sub.3pq in the grid of rows
q.sub.3 and columns p.sub.3 are arranged according to the rule
described repeatedly before; the parameters selected here are as
follows: .lamda..sub.3,1 . . . .lamda..sub.3,3 are wavelength
ranges for the colors red, green and blue (in this order);
n.sub.3m=3, and d 3 .times. pq = p 3 - ( p 3 .times. .times. mod
.times. .times. 3 ) q 3 ##EQU7##
[0333] Here, a filter element is, e.g., approximately 0.281 mm wide
and approximately 0.796 mm high. Other embodiments are also
feasible, of course. In FIG. 13, the color (i.e., wavelength)
filter elements are marked by an apostrophe (R', G' and B'), to
differentiate them from RGB pixels.
[0334] FIG. 14 shows a detail of the observer-side filter array
F.sub.2 of the third embodiment of the invention. Here,
b.sub.2max=4, with three transmission wavelengths or wavelength
ranges .lamda..sub.2,1, .lamda..sub.2,2, .lamda..sub.2,3 being
assigned to the transmission wavelength ranges red, green and blue
(in this order), whereas a fourth transmission wavelength range
.lamda..sub.2,4 completely blocks visible light. The coefficient
matrix d.sub.2pq is generated by the rule: d 2 .times. pq = p 2 - 1
- ( p 2 .times. .times. .times. mod .times. .times. 3 ) q 2 .times.
.delta. .function. ( ( p 2 + q 2 ) .times. .times. mod .times.
.times. 8 ) + ( p 2 - 4 q 2 ) .times. .delta. .function. [ .delta.
.function. ( ( p 2 + q 2 ) .times. .times. mod .times. .times. 8 )
] ##EQU8## in which n.sub.2m=8, and "mod" designates the residual
class with regard to a divisor. The function .delta. sets the value
"zero" for all arguments that are unequal to zero; the value of the
function resulting for the argument "zero" is 1, because
.delta.(0)=1 and .delta.(x.noteq.0)=0. The indices p.sub.2,q.sub.2
vary to adopt all possible values lying within the filter matrix to
be generated; these are, e.g., values from 1 to 3840 for p.sub.2,
and from 1 to 768 for q.sub.2. Here, a filter element is, e.g.,
approximately 0.285 mm wide and 0.804 mm high, other dimensions
being feasible as well.
[0335] Filter array F.sub.1 is arranged at a distance of z.sub.1=2
mm, and filter array F.sub.3 at a distance of z.sub.3=1 mm, behind
the projection screen. For filter array F.sub.2, the distance
z.sub.2=(-)45 mm; this array is located in front of the projection
screen (in viewing direction), which is indicated by the minus
sign.
[0336] If the projectors are aligned as described above, the image
structure produced is approximately like that shown as a detail in
FIG. 15. The grid with columns i and rows j has been drawn as a
reference only; of course it is not necessarily visible on the
projection screen 3. The image formed on the projection screen,
composed of different bits of partial information of the views
A.sub.k, thus shows a grid of image rendering elements
.alpha..sub.ij in columns i and rows j. The image rendering
elements .alpha..sub.ij may display light of altogether different
wavelength ranges, depending on what light is received from the
projectors at the respective spot of the projection screen. If, in
this exemplary embodiment, DMD/DLP projectors are used, the image
rendering elements here, because of the second projector-side
filter array F.sub.3, are no full-color pixels .alpha..sub.ij but
pixels that display, as a rule, light of the wavelength ranges for
red, green or blue. In FIG. 15 this is indicated by the columns
designated R, G and B.
[0337] Because of the light propagation directions defined by means
of filter array F.sub.2, an observer 5 will see, from every viewing
position, predominantly bits of partial information of a first
selection of views A.sub.k with one eye and predominantly bits of
partial information of a second selection with the other eye, so
that he will have a spatial impression from a multitude of viewing
positions.
[0338] Let it be noted here that, in this third exemplary
embodiment, too, the three filter arrays F.sub.1, F.sub.2 cannot be
made completely congruent by horizontally and/or vertically linear
scaling. In other words, the structures of the respective filter
arrays do not turn into each other by one- or two-dimensional
magnification or demagnification. With regard to the spatial
impression, this lack of congruence has the effect that the eye of
an observer will, from actually every viewpoint, always see a mix
of bits of partial information from several views.
[0339] The projection screen is translucent and preferably also
comprises a carrier substrate, e.g. a glass plate. In addition, it
may have a light-concentrating effect, i.e. a positive gain.
Excellent definition of the image rendering elements on the
projection screen is achieved if the projection screen is designed
as a very thin wafer, preferably with a thickness of less than one
millimeter. In this third embodiment, the projection screen 3 is a
flat plate.
[0340] Here again, the projectors used are furnished with image
data by an electronic control system, which may comprise one or
several separate units. Each of the filter arrays F.sub.1, F.sub.2
and F.sub.3 is designed as an exposed film. Each of them is
laminated onto a substrate, e.g., a glass substrate.
[0341] A fourth exemplary embodiment also uses an arrangement acc.
to FIG. 1; here again, eight projectors are used instead of the
four projectors on the drawing. Each of the eight projectors again
projects a complete 2D view of the scene or object, so that eight
views are displayed. Again, the optical axes of the projectors 4
intersect preferably at the face center of the projection screen 3,
with two neighboring optical axes including an angle of, e.g.,
approximately 3.5 degrees. The projectors 4 are aligned
accordingly, and their projection lenses have a distance of, e.g.,
2900 mm from the face center of the projection screen 3.
Advantageously, the projectors may be arranged on a circular arc,
the center of the circle being the said face center. Preferably,
all projector lenses are at the same height behind the projection
screen, viz. approximately at the height of the face center of the
projection screen. To ensure such a location, an appropriately
dimensioned mechanical tripod can be used, for example.
[0342] FIG. 16 illustrates a detail of the projector-side filter
array F.sub.1 of the fourth embodiment of the invention. The
wavelength filter elements .beta..sub.1pq in the raster of rows q,
and columns p.sub.1 are arranged according to the rule described
repeatedly before; the parameters selected here are as follows:
.lamda..sub.1,1 . . . .lamda..sub.1,4 and .lamda..sub.1,6 . . .
.lamda..sub.1,8 are wavelength ranges blocking the entire visible
spectrum, .lamda..sub.1,5 is a filter range transparent to the
visible spectrum; b.sub.1max=8, n.sub.1m=8, and d 1 .times. pq = p
1 - ( IntegerPart .function. ( p 1 + 2 .times. q 1 3 ) .times.
.times. mod .times. .times. 8 ) q 1 ##EQU9##
[0343] Here, a transparent or opaque filter element is, e.g.,
approximately 0.2847 mm wide and approximately 0.8044 mm high.
Other embodiments are also feasible, of course.
[0344] FIG. 17 shows a detail of the observer-side filter array
F.sub.2 of the fourth embodiment of the invention. .lamda..sub.2,4
. . . .lamda..sub.2,24 are wavelength ranges blocking the entire
visible spectrum; .lamda..sub.2,1 . . . .lamda..sub.2,3 are filter
ranges transparent to the visible spectrum; b.sub.2max=24,
n.sub.2m=24 and d 2 .times. pq = p 2 - ( IntegerPart .function. ( p
2 + 2 q 1 ) .times. .times. mod .times. .times. 24 ) q 2
##EQU10##
[0345] Here, a transparent or opaque filter element is, e.g.,
approximately 0.095 mm wide and approximately 0.804 mm high, other
dimensions being realistic as well.
[0346] Filter array F.sub.1 is arranged at a distance of z.sub.1=2
mm behind the projection screen. For array F.sub.2, the distance is
z.sub.2=(-)45 mm; this array is located in front of the projection
screen (in viewing direction), which is indicated by the minus
sign.
[0347] To improve the image contrast, the filter array F.sub.3,
which is located closest to the observer, is preferably provided
with an antireflection coating. This reduces reflections of
extraneous light and improves the visibility of the spatial
image.
[0348] If the projectors are aligned as described above, the image
structure produced is approximately like that shown as a detail in
FIG. 18. The grid with columns i and rows j has been drawn as a
reference only; of course it is not necessarily visible on the
projection screen 3. The image formed on the projection screen,
composed of different bits of partial information of the views
A.sub.k, thus shows a grid of image rendering elements
.alpha..sub.ij in columns i and rows j. The image rendering
elements .alpha..sub.ij may display light of altogether different
wavelength ranges, depending on what light is received from the
projectors at the respective spot of the projection screen. If, in
this exemplary embodiment, DMD/DLP projectors are used, the image
rendering elements are full-color pixels .alpha..sub.ij.
[0349] With correct alignment, the arrangement according to the
invention is particularly efficient with regard to the utilization
of the light and of the area, since every element of the projection
screen area can receive light from at least one of the projectors.
In this way, there will not be any "permanently black spots" on the
screen, so that every element of the projection screen area
displays some bit of partial information of at least one of the
views A.sub.k.
[0350] Because of the light propagation directions defined by means
of filter array F.sub.2, an observer 5 will see, from every viewing
position, predominantly bits of partial information of a first
selection of views A.sub.k with one eye and predominantly bits of
partial information of a second selection with the other eye, so
that he will have a spatial impression from a multitude of viewing
positions. FIG. 19 and FIG. 20 each show details of a possible mix
of views that can be seen by an observer's eye in a viewing
position if the first embodiment of the invention is used. In the
first position acc. to FIG. 19, the observer's eye will, e.g.,
predominantly see the views 1 and 2, whereas in the second example
position acc. to FIG. 20, it will predominantly see the views 4 and
5. If each of the observer's eyes sees one of the mixes of views,
the observer will have a spatial impression.
[0351] Let it be noted again that, in this fourth exemplary
embodiment, too, the three filter arrays F.sub.1, F.sub.2 cannot be
made completely congruent by horizontally and/or vertically linear
scaling. In other words, the structures of the respective filter
arrays do not turn into each other by one- or two-dimensional
magnification or demagnification. With regard to the spatial
impression, this lack of congruence has the effect that the eye of
an observer will, from actually every viewpoint, always see a mix
of bits of partial information from several views (see also the
view mix examples in FIG. 19 and FIG. 20). This completely excludes
the case that an observer's eye in any position in the viewing
space sees bits of partial information from exactly one of the
views.
[0352] The projection screen is translucent and preferably also
comprises a carrier substrate, e.g. a glass plate. In addition, it
may have a light-concentrating effect, i.e. a positive gain.
Excellent definition of the image rendering elements on the
projection screen is achieved if the projection screen is designed
as a very thin wafer, preferably with a thickness of less than one
millimeter. In this fourth embodiment, the projection screen is a
flat plate.
[0353] Here again, the projectors used are furnished with image
data by an electronic control system, which may comprise one or
several separate units. Each of the filter arrays F.sub.1 and
F.sub.2 is designed as an exposed film. Each of the filter arrays
F.sub.1, F.sub.2 is laminated onto a substrate, e.g., a glass
substrate. This provides for good mechanical stability. In the
arrangement acc. to FIG. 1, both filter arrays F.sub.1, F.sub.2 are
always arranged on the glass substrate sides facing the projectors
4.
[0354] A fifth exemplary embodiment also uses an arrangement acc.
to FIG. 1; here, however, only one projector is employed instead of
the four projectors 4 shown on the drawing. The projector is, e.g.,
a DMD/DLP projector and shows, in periodic succession, red, green
and blue images, with the red image corresponding to view A.sub.1
(k=1), the green one to view A.sub.2 (k=2), and the blue one to
view A.sub.3 (k=3). Altogether, n=3 views are presented.
[0355] The optical axis of the projector is preferably directed at
the face center of the projection screen 3. The projection lens has
a distance of, e.g., 2000 mm from the face center of the projection
screen 3. The projection lens is approximately at, or below, the
height of the face center of the projection screen.
[0356] FIG. 21 illustrates a detail of the projector-side filter
array F.sub.1 of the fifth embodiment of the invention. The
wavelength filter elements .beta..sub.1pq in the raster of rows
q.sub.1 and columns p.sub.1 are arranged according to the rule
described repeatedly before; the parameters selected here are as
follows: .lamda..sub.1,1 is a transmission wavelength range for
blue light, .lamda..sub.1,2 a transmission wavelength range for red
light, and .lamda..sub.1,3 a transmission wavelength range for
green light; b.sub.1max=3, n.sub.1m=3, and d.sub.1pq=-1=const.
Here, a filter element is, e.g., approximately 0.285 mm wide and
0.804 mm high. Other embodiments are also feasible, of course.
[0357] FIG. 22 shows a detail of the observer-side filter array
F.sub.2 of the fifth embodiment of the invention. The respective
parameters are: .lamda..sub.2,1 and .lamda..sub.2,3 are wavelength
ranges blocking the entire visible spectrum; .lamda..sub.2,2 is a
filter range transparent to the visible spectrum; b.sub.2max=3,
n.sub.2m=3, and d.sub.2pq=-1=const. Here again, a transparent or
opaque filter element is, e.g., approximately 0.285 mm wide and
0.804 mm high, other dimensions being feasible as well.
[0358] Filter array F.sub.1 is arranged at a distance of z.sub.1=2
mm behind the projection screen. For filter array F.sub.2, the
distance is z.sub.2=(-)45 mm; this array is located in front of the
projection screen (in viewing direction, which is indicated by the
minus sign. To improve the image contrast, the filter array
F.sub.2, which is located closest to the observer, is preferably
provided with an antireflection coating. This reduces reflections
of extraneous light and improves the visibility of the spatial
image.
[0359] If the projectors are aligned as described above, the image
structure produced is approximately like that shown as a detail in
FIG. 23. The grid with columns i and rows j has been drawn as a
reference only; of course it is not necessarily visible on the
projection screen 3. The image formed on the projection screen,
composed of different bits of partial information of the views
A.sub.k, thus shows a grid of image rendering elements
.alpha..sub.ij in columns i and rows j. The image rendering
elements .alpha..sub.ij display light of altogether different
wavelength ranges: in accordance with the geometry of arrangement,
the visible bits of partial information of view A.sub.1 (k=1) are
red, those of view A.sub.2 (k=2) are green, and those of view
A.sub.3 (k=3) are blue.
[0360] Because of the light propagation directions defined by means
of filter array F.sub.2, an observer 5 will see, from every viewing
position, predominantly bits of partial information of a first
selection of views A.sub.k with one eye and predominantly bits of
partial information of a second selection with the other eye, so
that he will have a spatial impression from a multitude of viewing
positions.
[0361] Let it be noted again that in this fifth exemplary
embodiments, too, the two filter arrays F.sub.1, F.sub.2 cannot be
made to be completely congruent by horizontal and/or vertical
linear scaling of their structures; her, in particular, this is
prevented by the specified different transmission wavelength ranges
of the two filter arrays F.sub.1, F.sub.2.
[0362] The projection screen is translucent and preferably also
comprises a carrier substrate, e.g. a glass plate. In addition, it
may have a light-concentrating effect, i.e. a positive gain.
Excellent definition of the image rendering elements on the
projection screen is achieved if the projection screen is designed
as a very thin wafer, preferably with a thickness of less than one
millimeter. In this fifth embodiment, the projection screen is a
flat plate.
[0363] Here again, the projector used is furnished with image data
by an electronic control system. Because of the spectral separation
of the views, it is recommendable that the control system is a PC
controlled by appropriate software. Each of the filter arrays
F.sub.1 and F.sub.2 is designed as an exposed film. Each of the
filter arrays F.sub.1, F.sub.2 is laminated onto a substrate, e.g.,
a glass substrate. This provides for good mechanical stability. In
the arrangement acc. to FIG. 1, both filter arrays F.sub.1, F.sub.2
are always arranged on the glass substrate sides facing the
projectors 4.
[0364] As mentioned before, it is possible to use, with all
described embodiment versions of the invention, filter elements not
only with the particularly preferable rectangular outlines but also
with other outlines. FIG. 24 shows various filter element outlines
that can be used in arrangements according to the invention; under
certain circumstances, a filter array may simultaneously contain
filter elements with at least two different outlines. Such outlines
can be used for avoiding moire effects. It may also be of advantage
if concave and convex filter element outlines are arranged in such
a way as to be interlocked. In this context, the term "dimensions"
of filter elements denotes the distances between the outermost
points in the horizontal and vertical directions.
[0365] Very special requirements with regard to image combination
structure or the specified light propagation directions can be met,
under certain circumstances, if individual filter elements
themselves have a transmission wavelength range in the form of a
graded-wavelength bandpass filter or a neutral density transmission
property in the form of a continuous neutral density wedge.
[0366] The invention is excellently useful in the fields of
entertainment (3D movies) and product presentation. The special
emphasis is on the fact that, depending on the embodiment, several
observers can view a large-size, brilliant 3D image with a fairly
large freedom of movement. The invention can be embodied with
components that are readily available or can be easily
manufactured.
[0367] FIG. 25 is a schematic, not-to-scale sketch illustrating the
principle design of an example arrangement according to the
invention with back-projection. Several (e.g., eight) projectors 2,
of which the drawing shows only four, are arranged behind a
holographic screen 1. Four of the image rendering elements 3 are
shown extremely magnified; they are struck by light coming from
different directions such as here, e.g., from different projectors
2. The image rendering elements of the holographic screen 3 display
the light rays in different light propagation directions 4. All
directions are drawn only schematically. In practical
implementation, the image rendering elements 3 would first be
significantly smaller than the dimensions of the entire holographic
screen 1, and they would be directly adjacent to each other, as a
rule. In FIG. 25, the neighboring image rendering elements 3 are
shown separated merely for greater clarity.
[0368] Here, each projector 2 projects, e.g., a (another)
two-dimensional view of a scene or object, so that altogether eight
views are projected. Thanks to the front-side light propagation
directions 4 for all light rays incident from the rear side,
defined by the holographic screen 1 or its imaging HOEs, an
observer 5 will see, from every viewing position, predominantly
bits of partial information of a first selection of views A.sub.k
with one eye and predominantly bits of partial information of a
second selection with the other eye, so that he will have a spatial
impression from a multitude of viewing positions. The viewing space
would be, e.g., to the right of the holographic screen 1.
[0369] As an example, each HOE could implement the optical imaging
effect according to item g) of the backprojection arrangement
according to the invention. A first filter structure for that
purpose, implemented by one or simultaneously several HOEs, could
be, e.g., the structure shown in FIG. 26 or a segment of it. At a
certain distance, e.g. 4 millimeters, the HOE, or each HOE, would
further implement a diffusely transparent opal screen. Finally,
another observer-side filter array structure would be provided
(e.g., at a distance of 4 millimeters), which is included in the
imaging effect of each individual HOE. FIG. 27 shows an example of
the last-named filter array structure.
[0370] For better understanding it may be noted that HOEs, of all
devices, are capable of storing and restoring information about an
entire spatial object to be implemented (here, e.g., a filter array
or part of it), even though they are considerably smaller than the
object to be implemented.
[0371] If, now, the eight projectors 2 project the eight different
views onto the holographic screen, the respective diffusing screens
implemented by the multitude of HOEs can be imagined to produce an
image combination structure of bits of image information, a detail
of which is shown in FIG. 28.
[0372] Further, the filter elements of the observer-side filter
array, implemented by the HOEs, again define front-side light
propagation directions, so that an observer's eye in a particular
viewing position would, e.g., predominantly see view 1, but also a
smaller amount of bits of partial image information of view 2, as
shown in FIG. 29.
[0373] From a corresponding viewing position, the observer's other
eye could then, looking at the holographic screen 1, e.g.,
predominantly see bits of partial image information of view 4 and a
smaller amount of bits of partial image information of view 5, as
shown in FIG. 30. Since either eye predominantly sees different
mixes of views, the observer has a 3d impression.
[0374] Another example of the effect of an HOE is shown
schematically in FIG. 31. An HOE of a holographic screen in an
arrangement according to the invention is shown at a high
magnification. The rear side of the said HOE is illuminated by
light rays incident from different directions and coming, e.g.,
from different projectors projecting different views. For each
incident light ray (the drawing shows only two, one being
represented by a solid line, the other by a broken line), the HOE
defines several light propagation directions as indicated in FIG.
31. If, for example, the solid line is a light ray representing
partial image information of view 1, and the broken line is a light
ray representing partial image information of view 2, here the HOE
would, for the shown incident light rays alone, define
approximately the light propagation directions drawn on the
observer side (on the right). If an observer moved along line 5,
which is shown with a perspective distortion here and actually lies
in a horizontal plane in front of holographic screen, he would see,
with one eye, first predominantly bits of partial image information
of view 1, then of view 2, and then, if further light rays (not
shown on the drawing) were provided representing bits of partial
image information of further views, e.g. views 3 through 8, he
would see further bits of partial image information predominantly
of views 3 through 8, until the cycle began again with view 1.
[0375] In this context, "predominantly" means that, according to
the invention, the multitude of HOEs define propagation directions
that cause an observer's eye to see, as a rule, not only bits of
partial image information of exactly one view. To demonstrate this,
many more of such HOEs would have to be shown in FIG. 31, but this
would make the illustration too confusing.
[0376] It is also within the scope of the invention that the light
propagation directions to be defined by the HOEs essentially
correspond to the respective light intensity maximums rather than
to non-divergent light rays alone. In this sense, e.g., also a
certain portion of the light of a light propagation direction shown
as a broken line in FIG. 31 would reach one (or several)
observation points actually lying in the light propagation
direction represented by the solid line. In this context, the light
propagation directions could be virtually interpreted as scatter
lobes rather than scatter lines. Preferably, the scatter lobes are
formed in such a way that an HOE, if it also implements, in any
position, a preferably diffusely scattering optical element, has a
light intensity maximum the course of which extends either
vertically or is inclined relative to the vertical.
[0377] FIG. 32 shows a model of an example illustrating the effect
of the HOEs on the holographic screen of arrangements according to
the invention. FIG. 32 shows a multitude of cylindrical lenses,
with each cylindrical lens being implemented by an HOE. This
corresponds to the imaging effect of the HOEs in accordance with
HOE feature a).
[0378] Characteristically in this example, the periods of the
cylindrical lenses are shifted relative to each other from row to
row by a distance that here, for example, is approximately one
third of the width of a lens (and, thus, of an HOE). One third also
corresponds to the non-integral offset relative to an HOE width
mentioned before. By means of such an imaging effect of the HOE, it
is possible to ensure that light propagation directions are defined
for incident light in such a way that, from every viewing position,
an observer will see predominantly bits of partial information of a
first selection of views A.sub.k with one eye and bits of partial
information of a second selection with the other eye, so that he
has a spatial impression from a multitude of viewing positions. Of
course, this requires that light from different views is projected
onto the rear side of the HOEs.
[0379] The imaging effect of the HOEs may further comprise that of
a diffusely scattering ground glass screen implemented on, or near,
the plane face of the grid of cylinder lenses (the lenticular).
[0380] FIG. 33 shows an exemplary image combination structure which
uses 4 views and can be used for an image back-projected onto the
holographic screen by, e.g., only one projector, to create a
spatial impression for observers in the fashion described above
(see description of FIG. 32). Here, every box corresponds to an
image point projected; the number in the box indicates the view
from which the respective image point obtains its image
information. The image points are arranged in rows j and columns
i.
[0381] The plane face of every cylindrical lens (and thus, the
projection of its convex surface onto the plane face) has, in one
direction, a length approximately equal to the height of a row of
image points of the projected image (on the ground glass screen
implemented) (e.g., 0.8 mm) and, in the other direction, a width
approximately equal to the width of four columns of image points of
the projected image (on the ground glass screen implemented) (e.g.,
3.2 mm).
[0382] Alternatively, the image combination structure acc. to FIG.
33 can be generated by projection of the four views by means of,
e.g., four projectors through a suitable filter array, which can
also be implemented by the HOEs.
[0383] FIG. 34 shows an exemplary model illustrating the effect of
the HOEs on the holographic screen of arrangements according to the
invention. For the sake of clarity, only a few HOEs are shown; for
the same reason, the rows of the grid are shown slightly staggered,
which is not required in practice. FIG. 34 shows a multitude of
cylindrical lenses and filter segments; each cylindrical lens and
each filter segment (especially if this is located between two
HOEs) is implemented by one HOE. This corresponds to the imaging
types according to HOE features a) and e). With regard to feature
e), different interpretations are possible: Either one HOE
implements several (here, e.g., two opaque and one transparent)
filter elements, or the different filter elements are implemented
by different neighboring HOEs. The optical effect is essentially
the same.
[0384] Each filter segment may, in addition, be provided with a
diffusely scattering area on its projection side, to be implemented
in addition by one HOE each. In this case also, bits of partial
image information are back-projected from several (e.g., four or
eight) views. For the said bits of partial image information of
different views, incident on the holographic screen, light
propagation directions are defined by the lenses or filter elements
simulated by the HOEs, so that a three-dimensional impression is
created.
[0385] The invention has important advantages over prior art. It
permits several observers to see an improved 3D image on a
projection system with considerable freedom of movement. Further,
the HOEs can implement optical images that cannot be practically
implemented with conventional optics unless incompletely or with
extreme technical expenditure. Moreover, it is possible to produce
3D projections of large images having dimensions, e.g., of several
meters.
[0386] Guideline parameters for the holographic 3D back-projection
disk to be used in connection with the arrangement according to the
invention are given below; they may be varied depending on the
application. In particular, the sizes of the angles .alpha. and
.beta. may be varied as required, in order to optimize the viewing
distance. Also, the degree of light transmission should be made as
high as possible.
[0387] FIG. 35 is a top view of a preferred embodiment version in
which a holographic backprojection 3D screen is used. It can be
seen that several projectors are arranged on a circular arc, with a
mean distance of approximately 2 m from the projection screen. The
angles .alpha. and .beta. are approximately 8.6.degree. and
approximately 0.83.degree., respectively.
[0388] The size of angle .beta. has been selected for a viewing
distance of 4.5 m between the observer's eyes and the projection
screen. As the angle .beta. is increased, the distance between the
viewing position and the projection screen decreases. From a
distance of 4.5 m, the observer's eyes can no longer resolve the
raster underlying the image information, which is favorable for 3D
perception. The raster size of the HOE on the projection screen
should be approximately 0.1 mm.times.0.1 mm.
[0389] In this arrangement it is possible, e.g., to arrange the
viewing positions (each of which corresponds to the eye positions
of one observer) either vertically as shown in FIG. 36, or
obliquely as shown in FIG. 37.
[0390] Identical viewing positions always offer identical mixes of
views. In every point of the curves shown, the summed shares of the
views yield a value of 1. Some leeway is permissible in smoothing
the curves or lines, which yields tolerances for manufacturing the
back-projection disk. Accordingly, the sum of shares may deviate
from 1 by a few percent.
[0391] The vertical arrangement of the viewing positions acc. to
FIG. 36 is preferably suitable for 3D movie theaters with a fixed
arrangement of seats, as viewing is independent of seat height. By
contrast, the oblique arrangement of viewing positions acc. to FIG.
37 is convenient for 3D perception by moving viewers. This is
essentially due to the fact that, because of the inclination, there
are no completely blind spots in the room.
[0392] FIG. 38 shows an embodiment of the arrangement according to
the invention with a holographic 3D back-projection screen which,
compared to the embodiment acc. to FIG. 35, needs only half the
number of projectors but nevertheless also ensures an excellent 3D
impression. Each of the projectors simultaneously projects
(interlaced column by column) two of the altogether eight images.
The distances of the projectors and the viewing positions from the
projection screen as well as the sizes of the angles are equal to
those of the embodiment acc. to FIG. 35. Here again, the viewing
positions may be aligned either vertically or obliquely, as shown
in FIG. 36 or FIG. 37, respectively.
[0393] In general, it should be noted that a slight mixing of the
views is advantageous for achieving a soft transition from view to
view.
[0394] As suggested before, the invention includes embodiments
permitting a choice between 2D and 3D projection. For switching
between the 2D and 3D modes, various embodiment versions are
possible.
[0395] If, e.g., a filter array is provided in front of a ground
glass screen and if these two components from a unit, this can
simply be reversed by 180.degree. in order to switch from 2d to 3D
display. In another version, this switching is achieved by changing
the position of the projector, or by deflecting the light coming
from the projector by means of reflectors.
[0396] If the arrangement comprises two filter arrays, these may be
arranged before or behind the ground glass screen and provided with
a sliding mechanism. Depending on the display mode desired, the
filter arrays are then slid into the imaging beam path or removed
from it. It is also feasible to make the structure of the filter
elements in the arrays changeable, e.g., by means of photochromic
or electrochromic layers or the like.
* * * * *